Fethullah Gulen and Erdogan were besties until about 3 years ago.
It's also a bit funny that you call this guy https://en.wikipedia.org/wiki/Fethullah_G%C3%BClen a Terrorist, if he is he has the best poker face of all of them so far.
While he probably has more than one agenda, neither the US, Israel nor any EU nation has never put him or his followers on any watch list, and at least publicly he strongly condemned any act of terrorism and incitement. He is such and "islamist" that he was probably the only major religious leader that didn't put the blame on Israel for the Flotilla incident and rather said that the organizers should have cooperated with them and put more effort into ensuring that radicals would not join the flotilla, this doesn't exactly seem like something a Terrorist would say publicly on several occasions and probably didn't made him any friends on either side of the political spectrum.
If you want here is a decent paper on him and his movement by the German Institute for International and Security Affairs https://www.swp-berlin.org/fileadmin/contents/products/resea...