Aside from that, Assad only recently changed tactics towards ISIS and then only slightly. ...
After which follows a baroque and florid conspiracy theory that I would have been ridiculed for.
Still, it has fans in the like of
David Blair (who is the guy who walked into one of Saddam's palaces after the Americans were done taking it and found documents saying that George Galloway had been taking money from Saddam).
On the other hand,
Patrick Cockburn favours the Saudi theory. I have read criticisms of that article and the Saudis have denied it, plus I have seen things purporting to support the theory you espouse, some of apparently sourced from the FSA.
It is possible that both narratives could hold some truth. Maybe the sacked Prince Bandar had miscalculated his ability to handle the export of Wahabism, perhaps Assad recognizes the value in having another enemy of the US backed FSA (remember, it's bad to interfere in a countries exercise of sovereignty by backing separatists, yes?), but he would also have to recognize the danger in that. Or maybe ISIS fights the weaker enemy to build itself up and Assad doesn't mind too much so lets them. Everyone risks blowback.
He should have intervened early on in the war, soon after Assad's forces opened fire on the protesters and while key Syrian army officers were defecting in numbers.
Like Russia should have intervened when Kiev started shooting protesters in the east and the entire eastern army defected to the separatists. Because THAT's what a real leader would have done, right?
Last time I checked both al-Qaeda and ISIS consider the house of Saud to be illegitimate and one of their main objectives is to topple it.
And yet, they haven't done much about that to date. Low priority perhaps.
Now, whether Saudi Arabia intended to make ISIS per se is another matter but they have had a long standing love affair with
funding their kind of religious nutcases. (Imagine what you could end up with if the US decided to give the Westboro Baptists billions of dollars provided they move to Russia). The Kingdom is only partly the House of Saud. They rule at the pleasure of the Imams to a large degree. The king has the money and the loyalty of the US, but the Imams own the people.
Anyway, with Bandar out of the picture maybe the Saudis are coming into line with the US policy of
funding the FSA. Still, while the government may be on side it's hard to stem the
private donations.