Another possibility is "he was about to do a mass purge of military & judges, & some of the military revolted in desperation". (https://twitter.com/davidgraeber/status/754417469641617412)

Could also be a hybrid: anyone in power in Turkey who pisses off enough people would expect a coup at any point, and therefore not only protect against it, but have a few ideas on how to greatly benefit. Like Saddam Hussein after failed coups.