Is it wrong to have a suspicion that many fighters are merceneries, working for whatever group funds them?
I think they migrate from ISIS, to Al Queda, to Muslim Brotherhood, to (moderate) Syrian Militants, to Syrian Army, to Iraqi Army, to Daish, to Kurds, to Turkish Army, to Taliban......
That absolutely happened in Afghanistan; a buyout of a supposed tribal ally allowed Bin Laden to escape Tora Bora. Family and tribal ties dominate rural and remote regions; I doubt some of those can actually conceive of a nation-state.
In more dense and urban areas tribal affiliation exerts less influence, but it is still significant.
This reported animosity between AQ and ISIS is more likely the swapping of allegiances among constituent tribes seeking better advantage or opportunities to avenge old slights.