And how’s that ‘acting’ working out for them and this administration so far?
From their point of view, pretty well. They seem to be able to attack anywhere, just not everywhere. They've killed members of the leadership from the nominal political executive on down. They've written down much of Iran's big ticket military equipment. They can, undeniably, cripple just about any Iranian vital infrastructure they choose. From their remarks, they pay attention to favourable domestic polling and disregard unfavourable. If they care about the economic impacts on much of the world and the attacks on other nations in the region, they do a good job of looking like they actually don't, much; instead, they use the ill effects as a cudgel to demand others join their windmill tilt. They believe that some of the foreign weaponry provided by Russia and China to various clients did not perform as advertised. They believe they've got China on the backfoot, and another project - Cuba - ready to go. Their usual anti-Trump neo-con critics are mostly silent on ends and limiting themselves to complaining about the way the administration went about it (Iran has been a wish-we-could neo-con project since before Iraq). They don't show evidence that they feel themselves bound to fix Iran after they break it, so all the what-iffing about the inevitability of boots on the ground and a long war and all the other assorted fretting might just have them shaking their heads and laughing. If things go badly, they'll do what they always do: point to their achievements, state that they decided that was enough for now, walk away, and shrug off the criticism by claiming their unwillingness to do "forever war" is a plus.
What they believe might be at odds with what others believe, but the political rhetoric about international order just doesn't seem to move them at all (if they're trying to change it, why would they respect what they're trying to replace?), and they ignore critics, especially those who respond emotionally.
Sadly them ‘winning’ in Iran will only service to embolden the incompetent donkeys running the place and God knows what occurs next.
I doubt the ability of the IRGC regime to simply shrug it off. Iran was under various kinds of strain; none of what is happening is making the situation better; its domestic problems are going to be exacerbated; the regime only knows how to squeeze harder. Some people believe it emerges stronger; I believe it continues sliding down.
"The defeat of the US is inevitable; they are fools; I don't know why they even try. Iran will emerge victorious, more powerful, more unified, blah blah blah." Wishful thinking isn't a failing of only the Trump administration.