Really, can you think of any reason why Democratic primary voters would prefer Bloomberg to Biden? Is he better qualified? Does he have more relevant experience? Is he a fresh young face? Is the party crying out for a billionaire nominee? Are his positions closer to the Democratic mainstream? Can he better appeal to white workers? Can he mobilize millennials and minority voters better? Is he, on the whole, more electable?
No.
The only reason to prefer Bloomberg to Biden is that he may be able to make a better case for realos than Biden does, particularly during the debates. That may peel a few voters away from Biden, but in reality, Bloomberg’s appeal is to NeverTrumper types who can’t or won’t vote in a Democratic primary, because they are Republicans or not affiliated.
The assumption is going to be that a Bloomberg candidacy will help Warren by splitting the realo vote. There will be a bit of that, but mostly, I think heated battles between Bloomberg and Warren will alleviate some of the pressure from Biden and put him in the middle, which is generally a good place to be. In short, this is not the disaster you might think at first glance.