bought in exchange for political capital
That’s a very uncharitable assumption of his motivations.
Dropping out of an (FPTP) primary is like awkward manual runoff voting. Once you clearly aren’t winning, you drop out so those votes can flow to the next preferred candidate.
People voting for Buttigieg switched to Biden because he was the most similar candidate. Of course Buttigieg would support the candidate that best matches his policy preferences – and the preferences of voters.
Does work for Tampa though