Once the snowball starts rolling, the later generations don't care much for the ridiculousness founding myths. It just becomes a traditional culture. Same for all religions, and heck, even nations
Whoever wrote the texts in the New Testament was clever enough to specify it vaguely. Short, for god, can be very long for you, mere mortal. Of course, there slipped an error in some of those texts where Jesus promised that this "short" means "within the lifetime" of those who he was speaking to. But, again, the Bible is so full of much more blatant inconsistencies that this got drowned down below. The believers don't mind, though...
The workaround for that "lifetime" bit is the claim that one or more of the people present were allowed to live forever. There is no end to the layers of explanations.
Its that part that gives meaning to meaningless life's. You are not just somewhere in the middle - another layer in the boneyard, you are the last generation. Being special.
Who knows. It's hard to tell at a 2000 year remove, when it's known that various scriptures have been heavily edited, redacted, etc. Mostly it seems like he was an early version of "Reform" Judaism that turned into a cult.
Beyond that, it's the entire history of the document, with the first 400 or so years being particularly amusing. To be clear, it's not like the same isn't true for other scriptures. You know that lovely story about Moses' birth? Just a ripoff of Sargon of Akkad's origin story, which was almost certainly not original.
People mostly believe what they want to believe.