According to the good folks at Wikipedia:
The madman theory was an important part of Richard Nixon's foreign policy. The madman theory was a feature of Richard Nixon's foreign policy. He and his administration tried to make the leaders of hostile Communist Bloc nations think Nixon was irrational and volatile.
Now that President Trump and his national security advisor have taken to provoking Iran, as they promised they would, one might think that Trump is taking a page from old Tricky Dick's playbook. I mean, what is more nuts than to push on religious fanatics to whom martyrdom is a happy goal and who only recently agreed to scuttle their nuclear program? Seems like something only a madman might consider.
Ah well. More red meat for the base. And the doomsday clock starts to tick more and more.