The problem is that Trump has spent his entire time in office flying in the face of rationality and political norms. The nuclear taboo since WW2 is just that, a political norm. The only thing that has ever prevented their use is that people did thought out the series of events that would follow and realized that it was a terrible idea.

Donald Trump has never heard a shitty idea he didn't like, and has never had the foresight or intellectual rigor to plan ahead. If there is anyone who thinks that he could break the nuclear taboo (or say, allow Israel to break it in lieu of doing it himself) it would be him, because he has never faced real consequences for anything at all up until this point.