Right. He's a wild card. He won't do well enough to emerge as a frontrunner, but he might do well enough to make Bernie's path to clear frontrunner status a lot more difficult. Especially as long as Warren remains in the running, splitting the progressive vote, and as long as Tulsi continues to run, not really standing any chance of her own, but likely siphoning votes from former Bernie and Yang bros.
Regarding late entries, I mean Iowa and New Hampshire weren't always all that important, and in the grand scheme, they don't provide a ton of delegates, so I think their importance is very overstated. RFK entered the 1968 race late in that year's primary, didn't even factor in to that year's NH contest. Yet prior to his assassination he was doing quite well in later primary states. Bloomberg seems to be adopting a similar strategy, totally ignoring Iowa and NH and instead funneling money and resources into upcoming states (many with higher delegate counts). Not to say he will do as well as RFK in 1968, but he might do better than anyone expects. Enough to throw a real wrench into the process. If he comes out of this with a large enough number of delegates, he can take that to the convention and affect the outcome for the other candidates. Even if he doesn't have enough to get himself nominated, it could still be a major factor in the eventual selection.