Any clue why the saudis are not handling iran ?
Simple. They’ll fight to the last American.
Right now the likelihood is that it would solidify support behind the mullahcracy. By way of parallel, the Iran-Iraq war of the 1980s that Saddam Hussein started, in an attempt to grab the Iranian oilfields, accomplished a few different things -- the immediate result being a massive reordering of Iranian society under a brutal Islamic dictatorship. In the longer term, feeding that many into the hungry guns led to a lost generation, a lost bloodline, of pro-mullah fanatics. Those who didn't serve, or didn't serve themselves to the guns at least, have descendants, while the fanatics mostly do not.
Also keep in mind that Arab armies are, uh, by and large, not the best in the world, and Iran's something like three to four times as populous as S.A. The renewal of US sanctions -- a policy that has always been strongly opposed by the mullah advocates, a list that includes Biden, Kerry, Hitlery, and Zero, as well as a few handfuls of FINOs -- undermines the Iranian ability to rule at home. Like the USSR years ago, the military, paramilitary, and terror budget has an insatiable appetite, and most Iranians don't support the regime. Unfortunately the Iranian public has been systematically disamred, and the mullahcracy has for decades propped itself up with "Palestinian" and other detritus that make up the thug forces that occupy Iran.
Iran's mullahs' supporters are easy to identify -- they support the Shiites, Houthi, and Alawi, when obviously, since all muzzies are enemies of this country, they should be in favor of continued war in and among all those countries, along with ZERO immigration of "refugees" (other than Christians fleeing the fighting). Instead, they support open borders, and the dictators and fake religious leaders (terrorists) of those three favoried groups.