What I am thinking, is that he has to have some motivation other than winning the Presidency as he certainly knows he has no chance at that. We know that he hates Trump and wants Trump out, so it just seems like this might be some calculated move to make that more likely. The two possibilities that sprung to mind when I heard this morning that he was running are:
1. He thinks that his candidacy will force the field to be more "moderate", ie softer on billionaires like him.
2. He thinks the current lack of a clear frontrunner will create a situation where Trump is able to limp back into the Presidency, therefore he is trying to kneecap Biden so Warren or Sanders can emerge as the frontrunner.
I can't really see what his game would be other than those two things... Unless its just straigthforward, delusional vanity.
Isn't it possible that he just needs this so as to prepare to run as an independent?
Cause the latter might still prevent a Bernie win against Trump (?).
After all, the same person threatened to run as independent back in 2016, if Hillary was not nominated. Not much changes with such people.