Selahattin Sevi / Zaman Daily News via EPA
Ironically, Gulen and his movement were allied with Erdoğan and his AKP years ago; each side operated on a platform of religious reformers pushing back against Turkey's longstanding secular-establishment elite in the early '00s, and Erdogan and his party needed Gulen's and his movement to get enough public support, to have the bodies to carry out purges of many of the secularists, to provide the manpower to replace those purged.
However, the more restrained and more moderately-Islamist Gulenists eventually became alarmed at Erdoğan's lurch towards authoritarianism and when they moved to prosecute close allies of Erdogan for very real corruption in 2013 (the largest corruption scandal in recent Turkish history), the two had a massive falling out, with Erdoğan's government since questionably labeling Gulen's movement as terrorist group.
It seems in Erdoğan's Turkey, there is no room for rivals or shared credit: in seeking to discredit Gulen's movement, Erdoğan is trying to rewrite the narrative of history that saw Gulen and his movement work hand in hand with Erdoğan and his AKP to reshape Turkey and wrest control of it from the secular elite establishment put in place by Ataturk when he founded the modern Turkish state from the post-WWI ashes of the Ottoman Empire; much like the ancient Roman occasional tradition of damnatio memoriae of trying to wipe disgraced (or sometimes just rival-to-the-new-ruler) figures from history, Erdoğan is seeing to it Gulen and his followers are removed from the story in any positive light, that only he and his AKP supporters ("the people," as the pro-Erdoğan language characterises them, as if there are not patriotic Turks who are against Erdoğan) will be seen as the founders, builders, and saviors of the new Turkey. As Orwell wrote in early 1944, "The really frightening thing about totalitarianism is not that it commits atrocities but that it attacks the concept of objective truth: it claims to control the past as well as the future."
Having now pushed Gulenists out of the public sphere and electrified his base, Turkey's president can rely on his supporters, then, to help stifle current and future dissent through social pressure, easing the burden on the government, which, of course, will still be there to use force when social pressure fails. The failed coup has given Erdoğan and his rather unlettered, chauvinist, now loudly-assertive AKP crowd the ability to control even more so Turkish education, police, courts, media, even the military--essentially, all the tools needed to have a stranglehold on societal mechanisms used to form public opinion--so that over time, the ease and ability to stridently go against the majority will be limited, indeed (in case you're wondering, the government already had a strong dominance over the country's clerical religious establishment). For Tocqueville:
Gulen's Extradition: A (Useful) Excuse for Anti-Americanism
"When an opinion has taken root among a democratic people and established itself in the minds of the bulk of the community, it afterwards persists by itself and is maintained without effort, because no one attacks it. Those who at first rejected it as false ultimately receive it as the general impression, and those who still dispute it in their hearts conceal their dissent; they are careful not to engage in a dangerous and useless conflict."
The fact that Gulen is living in Pennsylvania is extremely convenient for Erdoğan, who has decided to play the anti-Western, anti-American card for fairly full effect in Turkey. Most Turks actually think that the U.S. government was behind the coup, a belief amply fed by senior Turkish officials directly accusing the U.S. of supporting the coup, by wild reports in the Turkish media, and by even Erdoğan himself implying the U.S. at least supported it in some ways: the Turkish president went so far as to accuse a top U.S. general of "siding with coup plotters" and to exclaim that "This coup attempt has actors inside Turkey, but its script was written outside. Unfortunately, the West is supporting terrorism and stands by coup plotters" (ironic because it is Turkey that seems to actually be supporting terrorism, according to evidence). Such accusations made by Erdoğan are more or less red meat for his base, and he has been rhetorically issuing ultimatums to the U.S. government, offering a stark choice: hand Gulen over to Turkish authorities or lose your relationship with Turkey.
Erdoğan's repeated calls for the U.S. to hand Gulen over are basically a well-orchestrated ploy to drum up anti-Americanism in Turkey: the U.S., of course, will only seriously consider a formal extradition request with compelling evidence, and Erdoğan can keep repeating these calls without submitting a formal extradition request and keep fomenting anti-Americanism in the process. In fact, Turkish Prime Minister Binali Yıldırım even explicitly linked the future level of anti-Americanism in Turkey to whether or not the U.S. handed over Gulen, saying "Whether or not the anti-Americanism in Turkey will continue is "dependant on this." There is certainly some truth to this, but it is also hard to imagine Turks suddenly having a dramatically more favorable opinion of the U.S. just because the U.S. would hand over the government's prime suspect in a coup for which America is being blamed as a major player anyway.
What is certain is that there is no shortage of people who will be absolutely convinced that the U.S. is siding with Gulen and that it support the coup, and America not immediately handing him over only adds fuel to that fire. This is a winning situation for Erdoğan: he gets to keep fanning anti-Gulen and anti-American sentiment, and especially since Gulen is still safe in Pennsylvania, Erdoğan can keep Turkey on a crisis footing, allowing him to easily continue his abuse of power, since Gulen, shielded by American non-extradition, can be framed by Erdoğan as a continual threat justifying extreme measures. Clearly, then, Gulen is infinitely more useful to Erdoğan as a distant, U.S.-residing boogeyman than as a vanquished (possibly even executed) "traitor" in Turkey.
August 21st UPDATE: Thus far, while Turkey has submitted documents related to Gulen, the U.S. did not consider the first batch it has reviewed to comprise a formal extradition request, and, in the words of one Justice Department official, those documents only detail "allegations of certain alleged criminal activities that pre-date the coup" effort, that "[a]t this point, Turkish authorities have not put forward a formal extradition request based on evidence that he was involved in the coup" plot; in other words, zero evidence about Gulen's involvement in the failed coup has been provided.
While it is theoretically possible that Turkey will be able to provide a formal extradition request with evidence sufficient to merit the U.S. honoring an extradition request, I would wager that this will not happen. For one thing, there may be no such evidence in existence; another point to consider is that if Turkey did have such documents, Erdoğan and other Turkish officials would not likely be so intensely publicly pressuring the U.S. to hand Gulen over; if they had a rock-solid case, it would be an unnecessary rocking of the boat. Instead, because they are seeming to lack the appropriate evidence, Turkey's president may be hoping that his leverage on issues related to Syrian refugees, to ISIS, and to NATO will be enough to get the U.S. to cave in under pressure (thinking that is likely hubristic and a course of action that is not likely to happen without evidence).
Then again, maybe Erdoğan seeks anti-Americanism and drama with NATO for its own sake.In NATO Marriage, Erdoğan (Turkey's Putin) Flirts with Putin