Well, it should be noted that people left Rutherford's group in droves after 1925 in part because of his efforts to obtain complete control of affairs within ecclesias (which were led by elected elders who often continued Russellite teachings and disputed the "new light" coming out of Brooklyn). The decreases were not just the result of prophetic failure, although the failure of 1925 was definitely a part of the overall picture. So when Rutherford taught that the greater number of the anointed would fall away into apostasy, it rationalized the effects that his control tactics were having. The "theocracy" doctrine that Rutherford promulgated in 1938 effectively completed his pursuit of control of the "companies", making them all subsidery to the corporation. From 1927 to 1929, almost every other issue of the Watchtower had some discussion of congregational problems. Here is a sampling:
*** w27 9/15 pp. 280-281 Jehovah Alone Be Thy Fear ***
There are several ecclesias in the land wherein brethren who are acting as elders are opposing the service work. Whether they will ever get their eves open sufficiently to see their mistake the Lord knows. There are some members of the ecclesias that are being misled by these blind leaders that may get their eyes opened at a time when they will greatly regret that they followed men or feared men. The responsibility of each conseerated one is to his God. These are therefore warned not to be misled by men. It is gratifying however to note that there are not many of the opposers and not many classes will tolerate them long. This is evidenced by the fact that although a less number partook of the memorial in 1927 than heretofore, the reports show that there is a far greater number today actually in the field service work than ever before. It is a healthy sign.
*** w28 2/1 pp. 46-47 Suggestions ***
Loyalty to the channel is being claimed by many; but few there be that find it. It seems that boards are turning into "Sanhedrins," now and then "taking counsel" how they might "catch" some words and "cast out" the ones who are determined to fight the Devil's organization.... A mere claim of loyalty to the Tower is being made a deception, and the poor sheep cannot tell on which side one ought to be.
*** w28 11/1 pp. 325-327 Laodician Period ***
Elders in various ecclesias have said in substance this: "There is too much said in The Watch Tower about the Devil’s organization and about service; we should speak softly concerning the clergy and the nominal church lest we offend some therein; we do not approve of going from door to door and putting books in the hands of the people because that makes us appear as a book-selling concern and is a reproach upon the truth; we should develop beautiful characters; we should be developing love; we should meet together and study and meditate upon what is written in the Studies in the Scriptures because the Lord has revealed nothing to his church since 1916; we do not agree with what has appeared in The Watch Tower in recent years and we therefore advise the brethren to follow our example and to diligently pursue our Berean studies and to get ready to meet our Lord in heaven.’ On the face of it their speech has sounded plausible to many. It seemed to be an easier course to pursue, and therefore many have become lukewarm.... Some of those elaiming to be in present truth say, in substance, that ’all the light of God’s Word was published prior to 1917 and we have such and that is all we need’. Such is equivalent to saying: ’I am rich and increased in goods; I have achieved a good name and a splendid character; I have developed such a sweet character that it guarantees my salvation; I have a good record for activity in the past and there is no need for me to go from house to house telling others about the day of vengeance and the kingdom of God and unnecessarily bringing reproach upon the truth.’ Such are trying to convince themselves that they are right or "supposing that gain is godliness". (1 Tim. 6: 5) It will be observed that these usually claim to be better than their brethren, because more fully developed...They refuse to take a positive stand against the Devil’s organization, and to magnify the name of Jehovah before mankind, therefore they are neither cold nor hot....
When the lukewarm ones have due notice and refuse to be assimilated into the active working force of God’s organization which proclaims his praises, but rest on their laurels and their past record and their own goodness, the Lord declares he will vomit them out of his mouth as a disgusting and disapproved thing.... To claim that one by meditation and quietness can grow so sweet and gentle that the Lord will want to take him to heaven is a ruse of the adversary... An elder, who for some time has been made much of by the weaker ones of the ecclesia and who feels his importance, says: "I can not see that there is any greater light upon the divine plan being given the church now than we had twelve years ago, and therefore I am not in accord with the Society and the work it is doing." Such not only decline to actively participate in the service but advise others not to do so.
*** w28 11/1 To the Elders ***
Shortly thereafter a letter was received from an elder in a certain class and among others things in the letter it was stated, in substance, that in the class, of which the writer was a member, an elder made a speech saying that he did not approve what The Watch Tower said about the elders; that it looked to him very much like lambasting in the nominal system; and that after the elder had finished, another, who had just been elected, arose and severely criticized The Watch Tower, saying that The Tower was being used to set the elders up as targets and to ridicule them....
It seems to have pleased the Lord to have this done at the Society’s headquarters and that from there regulations are sent out to the various ecclesias. The elders in some ecclesias have not received these regulations joyfully, but, on the contrary, have resented them. Some elders say: "We are more important than the service director. As elders we will do as we please. We will not set aside our personality by getting in line and doing what headquarters has asked us to do, especially when that direction comes through a service director. We can not maintain our self-respect and so do." Now where such an attitude is manifested one of two things is absolutely certain: Either the Society is no part of God’s organization, and therefore has no right to issue instructions for action, or else the elders who take a position opposing are wrong in that opposition. If the Society is a part of God’s organization and it issues improper instructions, the Lord will correct these in due time. If an elder can not conscientiously comply with the instructions that are given, then he should remain quiet and let the Lord attend to any misstep of his servants. There is nothing in the Scriptures that warrants him in taking a position in opposition to the method arranged to carry out the witness work of Jehovah.... The Society formulates the plans of operation for the field work. Why does it do so ? Because God has placed the responsibility on his earthly organization to do a certain work, and some must arrange the mode of carrying out that work. The Society sends out directions in order that all the classes may work in harmony. Here and there in a class some elder rises and says: "No, we will not be governed by what comes from headquarters. We will conduct our part of the work to suit ourselves; we know how our work is to be done, and that is the way we are going to do it." Now for a moment let us suppose that every ecclesia in the land should be of that mind. What would result? Confusion and disorder, of course.....
And now a few words to the ecclesias. If brethren within our organization oppose the giving of the witness today, as outlined, if they counsel you against it, or if they fail or refuse to take advantage of opportunities to take the lead and encourage the brethren of the ecclesia in such work, then the responsibility rests upon you to ask them to step aside. If they oppose the service work you should at once pass a resolution and ask them to resign as elders because at once they show that they do not fill the requirements of the Scriptures as counselors, advisers, and ensamples to the flock. There is a responsibility resting upon all the members of the ecclesia. It is not for any ecclesia to honor and magnify men; but all ecclesias should honor and magnify the name of Jehovah God and his beloved Son, Christ Jesus. The time for quibbling is gone. The time for real action is here.
New converts were part of this struggle because they were more likely to be loyal to Rutherford than side with old-school Russellites. The rise in membership in the early 1930s would presumably have made it easier to vote problematic elders out of office (all baptized members can vote in congregational affairs). But by making all new converts second-class Christians without the spiritual authority that a spirit-begotten member would have, there would be benefits for Rutherford by having it that way as well, as it would make it harder for a convert to create trouble in local congregations led by anointed loyal to Rutherford.