I think this is what psychologically goes on in the minds of some. First, the neophyte is persuaded that several "core doctrines" are biblically sound and true (e.g. no Trinity, no hell, no immortal soul, Jehovah as God's name which should be widely used, a future paradise earth, etc.), the particular combination of which is held to be unique to JWs. These beliefs are used to define JWs as having the "true religion" (since they contrast as a group with the beliefs of other religions), and the arguments used to support them seem quite convincing to a learner. This is the "hook" because once the learner has accepted these teachings as true, he/she is easily guided to the conclusion that only the JWs have the truth and thus JWs are the "true religion". This makes some of the harder doctrines (such as "1914") easier to accept; the reasoning is that these teachings must be true since I already know they are right about other things and they are the only ones who teach these truths. Thus, the "core doctrines" help reinforce the veracity of other teachings that on themselves seem a little questionable.
The "sinker" comes when the idea is introduced that God has always had an organization and is himself organized. If JWs teach the truth and are the only true religion, then it is relatively easy to accept that the Watchtower Bible & Tract Society is "God's earthly organization". And once that idea is accepted, then any teaching stemming from the organization can be accepted as true, even if it has no biblical basis, such as the teachings about "1918" and "1935", or that the Society is to be identified as "faithful and discreet slave" in Matthew. And if the person has doubts about the validity of any teaching (e.g. that sure sounds like a stretch), the idea that the WT&BS is God's organization can resolve those doubts because one can reason that some day the Society will get it right with "new light" and it is up to Jehovah to update his flock with spiritual "food" at the proper time. Thus the very idea of "truth" itself becomes relative; what is "true" today may be false tomorrow, but until we have "new light" it is to be accepted as "truth". And the way the JW accepts Watchtower authority continues in a circular fashion around the same assumptions instilled early on, that only JWs teach certain true doctrines, that there has to be one religion on the earth that is "true" while all others are false, and since only JWs teach certain truths, they must be the true religion despite whatever "inaccuracies" or "mistakes" (which are not viewed as "untruths") they may make as imperfect men.
For instance, the idea that the "end is so close", reinforced by one's own perception of the current state of the world reported in the news, and the idea that there will be a worldwide preaching about the New System right before the "end" comes (based on a scripture), can combine to convince a JW that the Society is teaching the truth, for who else is preaching about Armageddon and giving a warning than the JWs right now? Similarly, the Society uses analogies from the OT to reinforce the idea that its organization is the only organization. One familiar trope is associating Armageddon with Noah's Flood (this is done through citing Jesus who compared Judgment Day with "the days of Noah"), and by likening the organization to the ark that saved Noah and his family. And this hits on the biggest factor for maintaning belief....fear. Fear of Armageddon helps keep doubts at bay because what if the Society is right? Even if one is no longer sure it is the truth, he/she may think that it's best to stay "in the ark" just in case. Also, the committed believe that eternal life at stake, for most JWs this means a most appealing future in a paradise Earth, without experiencing sickness and death. Many JWs desire this greatly, and thus emotion also plays an important factor...the belief or conviction that one will never die. One thus can have much at stake personally in this, and will want it all to be true, even if there are some doubts in the back of one's mind.
