Though they are attacking Turks now, its good to remember that ISIS is a Turk brainchild, the war in Syria is a Turk creation, that Turkey is ISIS’s safe rear-zone, it where they are supplied, its where their soldiers come through, its where they sell their oil (and specifically, to Erdogan’s son).
And that he has had State Department support all along. It was only once the PR problem became unbearable that Obama had to launch his pin-prick war and even at that he has done everything he can to protect ISIS.
So why would ISIS attack Turkey? Its like the joke about the scorpion. “I’m a scorpion, its what I do”. Islam is the only religion that the deeper you go, the more homicidal you become. If they can get to you, they would prefer to kill you. If they can’t, they’ll make do killing each other.
Quite correct — the Islamic state is the Turk’s brainchild, but the natural child of Saudi Arabia and Qatar (Wahabbi sunni jihadi states). These three Sunni powers wanted to kill the Shia, the Christians and the Alawites and Druze in Iraq and Syria.