Yes, markets weren't taking his "normal" market manipulation tweets seriously, so he had to go hyperbolic with the NUKE tweet. I am definitely sure Trump is not serious. That's why Iran said we will continue this discussion with complete distrust.
It is, but he is weakening the credibility of the United States in the process. Never make a threat you aren't willing to back, otherwise everyone knows you make idle threats.
It's just another military adventure ending in a disaster - probably the most humiliating in a long long time. But to your point, it's better for the US to admit defeat now, than in 2 or 3 weeks, let alone in 2 or 3 years. If a parallel can be made, Russia would have been best advised to have done the same 3 years ago.
It only requires reading your refusal to give a straight answer, eg your deflection to a passive-voice observation of the Roman Empire's collapse while avoiding the actual question of how you characterize an explicit threat to terminate a civilization.
