I'm not surprised at all that they closed. I had been there a few times and had a semi-pleasant time -- an interesting concept, but the food/drinks were nothing terribly special.
The last time I was there, the service was APPALLING. The two guys working the counter were incredibly rude and sassy. I actually heard them mocking me.
I've been to a past Istanbul Grille location, and I'm glad to hear they've taken it over! Hopefully they'll have some servers who aren't stuck-up hipster morons, unlike their predecessor...