This seems to be the most plausible explanation. The Gülenist elements in the military—and there are some, to be sure—most probably made common cause with dissatisfied secular officers against their common enemy. It is not surprising, therefore, that the government has been able to find enough Gülenists among the putschists to make the case that Fethullah Gülen was the chief architect of the coup attempt. This does not mean it was a Gülenist coup.…
Although at this stage it is difficult to provide a definite answer as to who plotted the coup, and with what goals in mind, one can reasonably surmise on the basis of fragmentary evidence and the history of earlier coups in Turkey that the hard-core secular officers [Kemalists] were most probably the dominant force in the attempted overthrow of the Erdoğan government, with some (one does not know how many) Gülenist officers acting in a supporting role.This would account for the widespread purge now underway in Turkey. This is basically the entire opposition. The coup has given Erdogan the pretext to decapitate it.
The National Interest
The Turkish Coup Wasn't an Inside Job
Mohammed Ayoob | Senior Fellow, Center for Global Policy, and University Distinguished Professor Emeritus of International Relations, Michigan State University