Couple thoughts on Iran. There are over 90 million people there. Only about half are Persian. Collapsing this regime would not be like taking down Libya (7.3m) or Syria (24m) or even Iraq (46m). The chaos could be larger, the refugee flows much larger - not good for the region or Europe, where many would go. If by chance a young ‘secular’ generation took over - it might also want a nuclear weapon. It was the Shah, after all, who started Iran down that path.
This is a point of divergence in interests between the USA and Israel. It isn’t in the interests of the USA to have a 2015 Syrian situation many times over. It’s definitely not in the interests of Europe, who would likely end up soaking up the refugees. But Israel might be content with a chaotic Iran that was just fundamentally incapable of challenging its regional power. People should be honest about such things.