Mister
Ignorance can be remedied. Stupidity is incurable.
Of course he didn’t have to do so when he did. That was his decision.
He and his team presumably believed it would give Biden the best chance to beat Trump and perhaps extract the most progressive concessions from Biden’s team.
Again why does it matter when he endorsed him?
AND “personal gain” not just “gain”
What did Bernie personally gain from endorsing Biden?
You claimed he endorsed him because of pledges signed. Those pledges apply to the nominee, not candidates. Biden is not the nominee yet. That's why it matters when. But you know that.
You made the claim without provocation. This was your doing.
What did Bernie gain by endorsing Biden? A seat at the table with Biden. Did you miss the tweets about their teams working together? Biden hasn't even been officially named the nominee. Is Bernie expecting more down the line, I'm sure that he is. And you'd be a lie if you say you don't think that's true.