Killed Iranian leader, Khamenei, wanted to be America’s enemy. He even admitted that he thought his revolution needed enmity with the US.
Usually, when violence ends an authoritarian regime, it results in a new authoritarian government.
If Iranians think the US is arming sectarian factions in order to break up Iran, even Iranians who are against the regime may join with the regime to defeat the US encouraging sectarian rebellions.