As I said...great. If Trump wants to carry the "you're corrupt and you are senile" torch, good on him. His faithful 40% eat that up, but the "give the outsider a chance" voters who put him into office are going to say "seriously?"
That's not what is going to happen. And "seriously", this is more than just 100% wishful thinking on your part.
Biden (if he gets a plurality, which now seems likely) will have a hard time defeating Trump. I think that Biden himself might have been ok with having Bernie as his VP, but the party won't allow it, thus making the chances of Biden as potus even worse.
Given a choice of who would be better, I would vote for Sanders. Trump only gets re-elected if the Sanders folks don't come out in force and vote Democratic.
The Bernie voters won't vote for Biden, unless Bernie is VP or similar. Ultimately, I think the election will be nearly impossible to win now. I do hope it will be won (but Biden as potus is already garbage, and without Bernie as VP why would the majority of Bernie voters help Biden?)