To answer the question, what they think would happen: Their October 7th attacked achieved everything they wanted.
KSA and Israel we're coming to an understanding and treaty, that was against the interests of Iran who is in a power struggle with the KSA.
After their attack, it is now politically impossible for the KSA and Israel to have a treaty. That alone justifies this entire conflict from their power politics perspective
They never had any hope of inflicting damage on the Israeli government. They clearly don't care about their own civilian casualties. In fact The worst the reprisals the better for their recruitment and funding efforts.
Probably not directly related to the rationale for their attack, but it got them some ancillary support, it removed Russia's aggression from the news media cycle. Which probably got them some favor in those circles.
From a media perspective, this has been a massive Boone for their campaign. They more or less had disappeared from international headlines for the last 10 years. Now everybody is talking about the genocide, and the ethnic cleansing. They're going to pay very dearly for it, but that's more media attention than they've had for a decade.