https://turkishinvitations.weebly.com/why-bill-clinton-mentioned-gulen-at-the-tccny-dinner.html
The presence of the President of Turkey, Abdullah Gul (who happens to be a close ally of Gulen) as well as a number of influential Turkish businessmen may have contributed to the attraction of the event.
However, the most probable reason for Bill Clinton's attendance was the Gulenists' numerous contributions to Hillary Clinton's campaign. A sampling is given in the Table below. All these contributions came from individuals identified as Gulenist based on their affiliations with Gulenist organizations or schools. This list is far from complete, and only represents the contributions that we have identified to date.
https://www.thedailybeast.com/alleged-coup-mastermind-fethullah-gulen-loves-hillary-clinton
The biggest foe of Turkey’s authoritarian president is a Hillary Clinton fan.
Fethullah Gülen, the Islamic scholar in self-exile whom Turkish President Recep Tayyip Erdoğan blamed for this weekend’s coup attempt, sung the former secretary of state’s praises to a small huddle of reporters who had gathered at his compound in the Poconos.
“I find her to be very courteous, very kind,” Gülen told The Daily Beast, speaking through his translator and spokesman. Gülen noted that he and Clinton had a brief face-to-face meeting during her previous Senate campaign.
“And before that meeting, some years ago, President [Bill] Clinton was facing a difficult situation here [in America],” he continued. “I wrote a letter to him encouraging him that he’s a successful president, and Hillary… actually wrote a response to that letter. So I find her to be very courteous and kind, and I find her to be of great hope for this country.”