Saudi Arabia and its allies are once again providing the ISIS breathing space by attacking its enemies. The Houthis had almost defeated the ISIS in Yemen. Now thanks to the Saudi strikes, the Islamist fighters are reclaiming the lost territories. Shameless Saudis.
I see it a little differently.
ISIS is like the wildcard in the region, there are the various governments and rebels, then somewhere in the wild, not supporting either side is ISIS.
When the Government and Rebels are strong, ISIS gets pushed back, but then the Government and Rebels clash, weakening each other and allowing ISIS to flourish. Once the fight between the Rebels and Government is over, they can both concentrate on ISIS again, pushing them back, until they choose to fight each other again!
ISIS isn't a big danger in the region, if a government really decided to do something about them, they could, but they seem content to mess round in various squabbles instead!