As he saw no chance to run for a Republican party that is happy with Trump he filed to run as a Democratic candidate. Bloomberg has since bought the Democratic Party in every state as well as the DNC:
The DNC told Mike Gravel they wouldn't change the debate rules for any candidate. "That's our #1 rule - we can't change the rules for anybody."
A few months later, they changed the debate rules to let oligarch Bloomberg into the debates... after he gave the DNC $300K.
He's dropping huge sums of money: on staff and resources, on TV advertisements, and on Facebook ads, where Trump has long dominated. And he's attempting to overcome his stodgy public image with the help of a meme army and through well-catered campaign events seemingly designed to convince voters that life under a wealthy technocrat might not be so bad. "I think it's classy," one supporter told the Times at a Philadelphia campaign rally complete drink station and a selection of cheesesteaks, hoagies, and brie-and-fig appetizers. "I feel like it's a nightclub in here. This is what he needs to get people going."