From what I read, oil production and export is pretty much uninterrupted. Everybody needs the dough.
That is why he took so long to take any action against them. We trained and armed them, but the trainers used were better than the ones to train the Iraqi's.
Both initially armed by us. Just Isis made better use of the training against the Iraqi's. They probably got field manuals on all the weapons and vehicles the captured from the Iraqi's. So it was no problem for them.