Iranian actions were previously constrained for fear of ending up in an all out war with the US, and they would moderate their response to provocations accordingly. But now Iran has stopped fearing a hypothetical war because it is already living in it. So the whole logic of being restrained no longer applies because you gain nothing by doing that when the US is already bombing the shit out of you. And since they have the upper hand, why not push all the way and remove the US from the region entirely. The alternative is to let the US rebuild, and face the same scenario as before the war again.