What I would like to know is where the WTs idea of the Great Crowd/Other Sheep came from? I know that during Russells time they believed that there were two classes going to heaven, then out of no where it seemed that a 'Jonadab' class was going to live on earth and they eventually became known as the Great Crowd of Other Sheep. How did this happen? Do you know where this idea started and why?
Ah, thereby hangs a tale!
The first premise is the 144k is a literal number and is cobbled together with Jesus' words in Luke 12 about his disciples being a 'little flock' (so it has to be an elite class, right?). But with an elite class among Christians, you have to provide a salvation plan for other Christians, believers down the ages and generally nice people. So Russell had an almost universalist approach to salvation but categorized people into several classes.
There were (source, p. 575-6 of the 1917 Finished Mystery):
Heavenly
- The priests/little flock/sons of God/spirit-begotten/'partakers of the divine nature.'
- The Levite class/great crowd/spirit-begotten but somehow fell short of their calling (negligent).
Earthly
- Ancient Worthies/faithful OT patriarchs and others who will be 'Princes' or leaders. It was once thought these may attain to the 'spirit plane' at the end of the 1000 years, but the idea was later ditched.
- 'Servants of the city' who will have certain duties.
- 'People of the kingdom'/resurrected Hebrews.
- 'Strangers'/millions of resurrected non-Jews who will not "have a part in the direct service of God."
Russell basically said the secondary heavenly class, the Great Crowd, could not be identified at present because it wouldn't be known who of the spirit-begotten class would turn out negligent. It would only be known 'beyond the veil.'
If memory serves, it was Rutherford who linked the antitypical Jonadab (companion of anointed Jehu) with the 'other sheep' of John 10 and the 'sheep' of Matthew 25 which was always an earthly class. And don't forget that Rutherford thought the separating of the 'sheep' from the 'goats' had been happening from 1918 onward when Jesus arrived and sat down on his judgment throne (the timing of that changed in 1994/5). He vehemently held that the Great Crowd was a heavenly class until at least 1932 (Vindication books).
In 1935, Rutherford totally changed his mind. At the summer convention, to which the Jonadabs were specially invited, he merged 2 classes - the earth-bound Jonadabs with the heaven-bound Great Crowd - and made them into one earthly class. His idea about the Matt. 25 separating work being fulfilled from 1918 onward underpinned his reasoning for this (see August 1935 WTs). Also, it was believed that the great tribulation was underway (the Great Crowd come out of this tribulation).
And so this other sheep/great crowd idea persists - even though it's no longer believed that Jesus has been separating the sheep from goats from 1918 (it's future), and even though it's no longer believed the tribulation is currently occurring (it's future), and even though the identified Great Crowd of 1935 has dwindled to a few.
Hope that helps to answer your question