Turkiye, while not an ally of ISIS, hopes to benefit from ISIS and its Caliphate. The Turks believe the Caliphate belongs in Istanbul but are constrained from proclaiming it themselves. If the ISIS folks can get their Caliphate established and accepted generally then Turkey will undertake to move it and the new Caliph to Istanbul not without opposition from the Arabs.
How's it working for the US and our regime change partners, when they try to take over Libya, Afganistan, Iraq, and Kiev from the people who did the fighting for them?
It's insane. ISIS is pure evil. Yet it seems that the power structure of the world, instead of disintegrating them is saying "what's in it for us"?