I think a major reason JWs make so many changes is a function of the huge number of dogmatic positions they take, over issues where they really don’t need to take dogmatic positions. It’s just part of JW culture now, to expect, and to receive, official judgements on minute points of Bible interpretation and life issues.
Take Matt 13:32 for example. As I recall the birds in this verse in Watchtower literature used to be agents of Satan. Whereas the latest Watchtower references insist that these birds are in fact rightly disposed humans.
On the other hand I once attended a Christadelphian Bible Study where the speaker suggested that the birds of this verse indicated a corrupting influence, whereas others in the ekklesia said they understood the birds as positive, and indicating the growth of the kingdom. There was open disagreement about the exact meaning, and no need for a dogmatic position to be adopted.
On minor issues like this, most churches simply don’t take a dogmatic position in the first place, so the issue of flip flops doesn’t arise.
So a major reason why JWs have so many flip flops is because they make so many dogmatic pronouncements on so many minor issues.