That upended the entire regional balance of power, driving all the Sunni states to seek stronger alliances amongst themselves and against the Shiite bloc. And it's led Iran to continue to push and prod that new bloc using their proxy paramilitary organizations.

Iran using their proxies to spread terror around the globe pre-dates Gulf War II. The mismanagement of the immediate aftermath of the invasion along with the decision to just pull up stakes and leave without first vastly reducing Iran's ability to influence/destabilize the new Iraqi government didn't help.

High oil prices and the effective dissolution of the political power of OPEC (does anyone ever talk about them any more?) are giving the Iranians more economic power than they should have, given the sanctions in place on their economy.

There's a macabre foreign policy game of "Just the tip" (hat tip to Ben Shapiro) playing out right now. It goes something like this

*Iranian proxy does something (in this case, Hezbollah blows up a schoolyard full of kids)
*The Israelis retaliate, often in a way that embarrasses Iran (like showing the ability to blow up the bed of an honored guest)
*Iran is then allowed some measure of "retaliation" even if it amounts to not much, they get to say they did something

On some levels it makes some practical sense...until one stops and thinks that the best scenario is one where Iran doesn't encourage its proxy goons to stir up stuff in the first place.