Is Trump really trying to appear to the Iranians as being irrational here as a negotiation strategy? Is he saying "don't mess with me I'm crazy"? I would counter that he is aggressive and rational. He is saying I am willing to use force and he uses force. His use of force feels fairly rational within the stated goals of forcing Iran to give up their nuclear weapon program (as a minimum short term objective) with maximalists goals of either replacing the regime or removing their offensive capabilities.
If this is irrational, what does a rational use of force look like? Do we agree that without the use of force Iran wouldn't give up their nuclear weapons program? What is true is that the use of force has consequences and of course it would be better to accomplish your objectives without the use of force. Why can't we all get along sort of thing. But Trump (and not just him, many people around him) believe there is no path that doesn't involve the use of force. They tried a bit before and they seem to be trying now before using even more force. I happen to agree there was no path that doesn't involve the use of force and likely more force is going to be needed. The Iranian "we can't agree because we don't trust the US" is an obvious lie aimed at those who oppose US policy (both in the US and out of the US".
All that said, there is still a question of whether the US is willing to use enough force over a long enough duration to accomplish its goals. If the end result is force use, price paid, and a nuclear Iran with long range ballistic missiles, then it's a pretty bad outcome. This is the outcome many are pushing for.
EDIT: In terms of the Iranian lies. If they are saying we can't agree to "suspend our nuclear program for 10 years" because the US and Israel will promise not to attack us and then they will - they are absolutely right. The US and Israel will attack them. That's not a "trust" or rationality issue. We know the Iranians won't keep this agreement because they haven't kept any agreement. We know they won't allow the IAEA random inspections of any site and even if they did they're capable of hiding their activities. The problem is they are not sincere. If they were sincere they would offer and keep the conditions that ensure that they will not be attacked. If they actually suspend their nuclear program (doubtful) and instead build 100k conventional ballistic missiles that's a threat to Israel that is equal to the nuclear threat. And so ofcourse they would be attacked. For them not be attacked they need to actually give up on the religious/ideological ideas and they can't. You might say this is a very opinionated take but it's backed by evidence and with what Iran says on these topics.
