That's always a perilous arrangement, particularly with authoritarian states. We made a similar play with the Taliban against the USSR during the '80's as I recall. If I were in Israel's shoes, I wouldn't trust the Saudis.

It's also worth noting that Iran has its own friends, not just in the region but internationally as well. The Syrian gov, Russia, Yemeni Houthis, LH just to name a few.