Frankly, the only thing that makes sense is that Ohtani was absolutely in the know about the money going to the bookie. And as seems to be the consensus, the best story for Ohtani was actually the first one, that he did it to bail out a friend, even if that story has some nasty legal consequences of its own.
Between this and Yamamoto giving up 5 runs in an inning, that was one heck of a bad day for the Dodgers.