The motivation is obvious:
The use of the Islamic practice of taqiyya or deception to mask the true nature of the schools has been upheld by Gulen himself. In a 1999 sermon, the Turkish pasha offered the following advice to his followers:
You must move in the arteries of the system without anyone noticing your existence until you reach all the power centers … until the conditions are ripe, they [the followers] must continue like this. If they do something prematurely, the world will crush our heads, and Muslims will suffer everywhere, like in the tragedies in Algeria, like in 1982 [in] Syria … like in the yearly disasters and tragedies in Egypt. The time is not yet right. You must wait for the time when you are complete and conditions are ripe, until we can shoulder the entire world and carry it … You must wait until such time as you have gotten all the state power, until you have brought to your side all the power of the constitutional institutions in Turkey … Until that time, any step taken would be too early—like breaking an egg without waiting the full forty days for it to hatch. It would be like killing the chick inside. The work to be done is [in] confronting the world. Now, I have expressed my feelings and thoughts to you all -in confidence … trusting your loyalty and secrecy. I know that when you leave here - [just] as you discard your empty juice boxes, you must discard the thoughts and the feelings that I expressed here.