I knew this was suspected but I thought it was officially denied. Apparently it's acknowledged by the Saudis. This quote from a recent FT article [0] surprised me:
After the Iraqi city of Mosul fell to a lightning Isis offensive in 2014, even
the late Prince Saud al-Faisal, the respected Saudi foreign minister,
remonstrated with John Kerry, US secretary of state, that “Daesh [Isis] is our
[Sunni] response to your support for the Da’wa” — the Tehran-aligned Shia
Islamist ruling party of Iraq.
If you invest a lot of time, whether it's configuring your .vimrc/.emacs.d/init.el or throwing a lot of money at a specific car/tool brand, you're naturally going to have an emotional attachment with that. Read the comments on tool reviews on youtube - contractors have holy wars over their DeWalts vs Milkwakees. Slashdot in the mid 90s was emacs vs vim/GNOME2 vs KDE3 for the better part of a decade. It's not limited to only the Perl greybeards or contractors - it's quite common for tenured professors to be ousted as complete frauds after some other lab tries to replicate the findings only to yield entirely different results. "The results should have yielded this, so .." This is human nature - people are going to inherently defend anything they invested a lot of time in learning/using/doing.
With religion, it's 10x more intense because they can't put down the beaker or drill and go have a beer with their buddies - it's their entire identity. FT/Der Spiegel/The Guardian(usually)/the Newshours(BBC/PBS) all do a good job for the limited amount of time/column-lines they have to cover such a complicated topic such as religious factionism that goes back thousands of years. Then there's the Bismarckian Realpolitik which is certainly a large aspect of it.
There was certainly Saudi money behind it. But when you hear "state-sponsored terrorism" it could mean a lot of things. A governor or 8th son might have funded a non-profit NGO which later turned out to be mostly legitimate but 10% of those funds were diverted to purchase New-old-stock over-stock arms from the former USSR (then the question arises - was it with or without his knowledge?). because the House of Saud itself has politics that are so intricate internally that you'd have to spend years studying that exclusively. Start reading about the First Saudi state of 1744 (under Abdel Wahhab's rule in alliance with ibn Saud) and a few thousand pages later one might have half of a grasp on the internal politics. And that's just historical internal Saudi politics. Bring in religious subsets and hatred spawned from that, ethnic hatred (Persians are about as Arab, as Japanese are Chinese), international interests propping up different regimes and it's all a very complicated game.
Think of how complicated our government operates with just two parties - the capitalists who retain the lobbyists that influence the congressmen who have multiple interests that have to be simultaneously balanced in order to keep their constituents, donors, and party all happy enough so that you retain power. It's all a subtle game of spinning plates and we're working with just with two parties (effectively).
This. I think the fundamental human inability to acknowledge and anticipate the complex forces that drive an opponent was evolutionarily handy in the savannah, but is now quite the handicap in navigating geopolitics. This is something that mainstream media is adept at - describing Iran or China as a monolithic malevolent force plotting evil against the rest of the world might be elegant from a Manichean perspective (e.g. "Iran called off talks", "China moved its ships to the Spratly Islands", etc.), but does not do enough justice to the mind-boggling complexity of these ancient societies.
