I think the whole “Gods Will” thing gets overplayed in the West. As is sometimes the case I think a lot of it stemmed from something Jeremy Clarkson said once.
People in the Middle East aren’t as risk adverse as us in the West, but few places, if any are as risk adverse as us. You will find people in the ME who will wear seat belts and take all manner of other precautions without worrying their God will strike them down for messing with his plans.
As for why they don’t wear Helmets, a little of the above I guess.
Another factor is cost, AK style rifles knocked out in China or AR style rifles donated from the US are very cheap and they cover the most basic requirements for them to be able to kill people at a distance. If you’re working to a limited budget it’s guns first, protection second.
Also, they’re not really designed to be bullet proof, even the very fancy ones Western Armies use are useless against a direct hit from an assault rifle – they’re more for protection from falling debris and solders banging their heads climbing around cover etc. You might recall if you’ve seen Black Hawk Down, some of the Solders wore Ice Hockey Helmets as they did 90% of what the Kevlar helmets did, whilst not being so hot or balky.