It is also a main objective for China, draw US in and bleed them dry.You say the aim is Iran, but the end game is China or Russia. So by that logic, why would Russia and China sit by and let this happen.
I think there's a reason both US or Israel are cautious about taking on Hezbollah. Consider just for a second how weak the response has been so far: IDF has lost more than a dozen tanks and nearly a 100 soldiers to Hezbollah cross border strikes. Imagine if Russian units fired at polish troops and killed dozens. Or ROC soldiers launched atgm at Fujian bases and destroyed over 10 tanks. Wouldn't it be a laughably weak response for the recipient to not immediately declare war?
US still has a working strategic planning apparatus and they're trying not to fall into the pit. But it will be increasingly difficult the more they get provoked.