ISIS basically tied the hands of Syrian and Iraqi Kurds and prevented them from being able to exert any political or military pressure on Turkey and other contested territories.
For Tureky it's a win win, either ISIS crushes the Kurds or creates enough mess for Turkey to get involved and hen it can bomb the Kurds just as much as they bomb ISIS if not more.
People don't have visibility into that conflict as much as they do in others since Turkey seems to be able to keep a much better lid on the media and there seem to be far fewer Kurdish lobbies in the west than for some other groups.