ISIS was founded earlier, yes, but it only became so "successful" because of Ba'athist officers who were little more than mercenaries with no place to go after the dissolution of Sadam's regime. They needed to survive somehow and so many ended up going to ISIS that it turned into a full blown military force with fully trained Iraqi officers, all of them veterans of at least one war, with tons of left over American and NATO hardware.

I won't go so far as to say that the whole fiasco could have been avoided with a functioning economy and some new civil service/protection branch to absorb the officers, but the US's strategy was one of the biggest contributors to ISIS's growth.