This war is a reaction by Iran against the Saudi peace initiative toward Israel. Iran can't have peace in the middle east - that would hurt its position as supporter of islamic revolution. Plus, they really hate Jews and don't think Muslims should associate with Jews. Esp Saudis because Mecca.
Also, Russia is putting the squeeze on NATO from Ukraine, Africa (Russia is supporting coups in the Sahel), and now the middle-east. Draw that on a map and Europe is getting surrounded by chaos. Ukraine, Middle East, Africa.
the keys now: the war is over. Israel should try very hard not to get baited into crimes against humanity trying to root out Hamas. The civilized world is on their side. Israel will most likely blow it by killing lots of Arab civilians, but maybe they won't. The war is over. Israel needs to chill a bit and let the civilized world come together. Not blow up all this good will.
The US has to gather the civilized world and work at eliminating Hamas, isolating Iran and helping Saudi to find a way back toward peace with Israel. Biden is pretty good at that. I'm confident.