Hasn't he almost always been like that? It just helped that it wasn't aimed at users before, but either controversial people, or something that could at least be excused.
His database-editing negative comments talking about him wasn't anything less controversial, or indicative of a thick skin.
It might be less his "saving Reddit", and more Elon Musk and Twitter that might be doing it. He basically proved that as a billionaire CEO, you can waltz in and do whatever you like. Even if it's unpopular, a big platform (like Twitter) isn't going to implode immediately, so he can just squeeze out what money he can, and make out reasonably wealthy (or at least, that's the idea), in spite of user unpopularity. "Saving Reddit" seems more like a flimsy justification.