I suspect Saudi Arabia already had it's political agenda against Qatar and Trump's recent visit and support emboldened them to act. That Trump's tweets support the narrative that they were acting to curb extremism and terrorism just played into their laps. They probably couldn't believe their good fortune. Add in further interference by Russian hackers and you can see how easy it is to turn the middle eastern nations against themselves. They should be unified in their goals but the jostle to be the main power broker in the region keeps them at each other's throats.