I think Warren showed us why Bloomberg is there. He is a Trump stand in to use during the primaries. The attacks can simply be used to distract from the dems message on everything while practicing for the general election. Her "and I'm not talking about Donald Trump" line says a lot.
I think whoever said, "Bloomberg is in the race to spend as much as he wants against Trump without breaking campaign finance law" is correct. Trump doesn't care about campaign finance law or many other laws because he is unidictable.