1. That would make Jesus (a Jew) wrong, not Christians as a class.
2. I see no logical way to draw that from the Bible. I'll have to ask gfm7175 about this. He's my go-to expert on Biblical matters. I'll find out and get back to you.
I know a lot about the Bible, actually. There's a group on Reddit called r/academicbiblical, and I email with a couple of the moderators there. (You can't be a moderator there unless you have verifiable credentials in this area.)
Regarding Jesus as a failed end-times preacher, the New Testament is full of evidence of early Christians coping with the failure of Jesus’ promise to return with their own generation.
During his mission, Jesus proclaimed that the Kingdom would arrive within his generation, probably while his disciples were still alive (Mark 1:15, 13:30; Matt 10:7).
When Christians began to die decades following the crucifixion, Paul and others coped with the anxiety of the delay by stating that some would still be alive (1 Thess. 4:15-17; Mark 9:1), including the high priest (Mark 14:62).
To deal with the delay, the author of Luke tones down Mark by removing “in power” in Mark 9:1. This is because for Luke the Kingdom has already “come to you” in Jesus’ own ministry (11:10). He also changes Mark 14:62 since the high priest was long dead (Luke 22:69).
When almost the entire first generation had died, “rumor spread in the community” that one disciple would still remain when the Kingdom arrived (John 21:22-23)
Then he too died, so it must have been that “Jesus did not say that he would not die.” Increase in delay caused “scoffers will come…saying, ‘Where is the promise of his coming? For ever since our ancestors died, all things continue as they were from the beginning of creation!” New arguments of defense arose, such as our concept of time being irrelevant because “With the Lord one day is as a thousand years, and a thousand years as one day” (2 Peter 3:3-8).
The author of John uses the “spiritual” tactic seen so often in apocalyptic movements following a delay. In short, the earthly kingdom is now a spiritual one, available in the present for all who are “born from above” (3:3, 5). The apocalyptic message about a coming Son of Man is absent.
By the time the Gospel of Thomas was written, a future kingdom is completely rejected by many Christians. “Rather, the (Father’s) kingdom is within you and it is outside you,” and “is spread out upon the earth, and people don’t see it” (Thom 3, 113; see also 18).