The Arab Spring uprisings had shown Gulf monarchs that popular anger over repression and corruption were bigger threats to their rule than any blowback over their failure to maintain solidarity with the Palestinians.
Other events changed their security calculus. Washington stood by as a staunch ally, President Hosni Mubarak of Egypt, was ousted in a popular uprising, and failed to respond militarily when Syria gassed its own people and Iran was blamed for an attack on Saudi oil facilities.
It became increasingly clear to the Gulf states that the Western allies they had relied on for decades to come to their rescue might not be there in a pinch.
Finally, as Iranian-sponsored proxy forces grew more powerful across the region — in Lebanon, Syria, Iraq and Yemen — the Gulf states increasingly saw Iran as their greatest threat. And the 2015 Iran nuclear deal persuaded them that Washington was not committed to destroying Iran’s nuclear ambitions or keeping Iran pinned down by sanctions.