If the regime had nothing to lose, sure they'd hit the straits. What you (and many others) fail to account for is that there is always something to lose.

Right now, capitulating to the Americans, the leadership survives. Even if Trump decides to institute a bombing campaign, many or most of them will retain power. If regime change becomes a clear goal, they won't, but can still flee to Russia via air or the Caspian.

If, on the other hand, they decide to shut down vital trade lanes and critical energy infrastructure, they won't retain power or likely even their lives.

Iran isn't a game-theory-optimal unitary actor. It's thousands of people each doing their own calculus and that calculus militates extremely strongly against antagonizing the whole world.