Two pieces of evidence for you to peruse. First, it turns out that there are proportionally a whole lot of Saudis working for Daesh as suicide bombers:
UPDATED: 31 suicide bombers in #Iraq in 45 days 46% of them are Saudis. Over 50 tons of explosives used. pic.twitter.com/L49jhLazow
— Zaid Benjamin (@zaidbenjamin) October 18, 2014
Though McClatchy’s Mitchell Prothero has an easy explanation for that figure:
@jonleeanderson @zaidbenjamin It’s standard. Saudis tend to be fat, lack military training and thus have little value to jihadis otherwise.
— Mitchell Prothero (@mitchprothero) October 18, 2014
@jonleeanderson @zaidbenjamin and I’m not even being mean there was literally a memo from AQ in Iraq about it back in like 2005.
— Mitchell Prothero (@mitchprothero) October 18, 2014
Still, lots of Saudis in Daesh doing terrible things. Our second piece of evidence is that there’s apparently a considerable amount of popular support, or at least sympathy, in Jordan for the terrible things that Daesh does, and even more popular sympathy for Al Qaeda:
But not everyone in Jordan supports membership in the coalition. According to a poll published last month by the Center for Strategic Studies at University of Jordan, only 62 percent of Jordanians consider IS—and a mere 31 percent the Syria-based Al Qaeda affiliate Jabhat Al Nusra—to be terrorist organizations. Even more stunning, just 44 percent of Jordanians surveyed say that Al Qaeda is a terrorist group.
Given these sentiments, it’s not surprising that many Jordanians oppose their military’s participation in the campaign targeting IS and Jabhat Al Nusra.
In fact, objections to a Jordanian role in the anti-IS alliance emerged before the state signed up. In the beginning of September, twenty-one members of Jordan’s parliament sent a memo to its speaker rejecting the Kingdom’s participation. “This war is not our war,” the representatives wrote. “Our army is able to defend our borders and respond to any aggression.”
Now call me crazy, but do you think there might be something about these two Western-aligned, autocratic monarchies that routinely suppress dissent and stifle individual freedoms that would cause elements of their populations to sympathize with the aims of a group like Al Qaeda or Daesh? I feel strongly that there might be a common thread here, but I just can’t quite figure out what it could be.
Oh yeah, of course, DUUH! Thanks, Sam! There’s nothing else that’s similar about Saudi Arabia and Jordan in any way that could explain it!
The Foreign Exchanges Companion 
I laughed, I cried, I guzzled a fifth of Maker’s Marker and turned to the neuroscientists for answers to every vexing problem. Corrosion chemistry, that’s awfully vexing. Then I ate a handful of Valium to finish the job.