Yep. It's a bit like the theory that scammers mention they're from Nigeria because they're ingeniously weeding out all the people who've heard of the scam before, and not because they need an excuse for people to send money to Nigeria (and with their culture and education level the ALLCAPS and religious references look very official and honest indeed), and if the cost of that is that 99.99% of their emails don't get delivered due to automatic filters protecting even the most gullible of recipients, well that's probably not something they've given much thought to.
I've read one interview with a scammer who mentioned that the initial pitch is deliberately written that way to screen for gullible people, and I've read extended email exchanges with Nigerian scammers where their broken English becomes flawless after the initial reply. 419eater.com was a treasure.
These days though, like most scams the 419 scams have been taken over by organized crime and worse. The average Nigerian scammer nowadays is probably doing it because Boko Haram will kill their family if they don't.
419eater is also full of scammers whose English notably deteriorates, scammers who have almost endless time to comply with bonkers requests, and scammers that are quite far into the discussion when they go to some effort to produce "official documents" that look like they were produced by a child. And personally, I've experienced the reverse, where even when it's a well constructed item-for-sale scam by someone with access to a PayPal account they can't help but use email addresses that look a bit too Nigerian to be an elderly Scottish lady and English that just doesn't match the ad copy and is obsessed with explaining the safety and urgency of the transaction rather than the "product". Most of the others have to mention Western Union to Nigeria at some point...
Just doesn't make much sense for people whose time is valued in cents per hour and whose theoretical earnings are in the thousands to optimise for screening out non-gullible people, plus the 99.9% of gullible people that have some sort of spam filter in the loop. But hey, if someone's shared that Microsoft Research paper with the scammers and they've come to believe that using formats that almost invariably bump into spam filters is actually a shrewd move on their part, who am I to discourage them?!
I don't know about Boko Haram involvement, but I assume the organized crime guys have some sort of MLM-style operation scamming Nigerians into paying for the get-rich-quick opportunity.
