A point of clarification
Saudi Arabia is not bombing Daesh in Yemen. As a previous comment has pointed out, ISIS is not that far, ideologically, from the government of Saudi Arabia (and if you go back to the formation of the Saudi state from 1800 - 1940 there are some interesting parallels).
Nothing lines up perfectly, but what is happening in Yemen is part of the larger Saudi-Iran conflict. Saudi Arabia is supporting the Sunni-ish government against the Houthi (Shia-ish, therefore Iran-backed) rebels, who themselves are largely a tool of the previous Yemeni president.
Meanwhile in Iraq and Syria ...