80-20 it’s a misguided missile attack on either a falsely identified target or a plane that happened to get into a flight path for a missile going after a higher target.
The other possibility is an onboard bomb that exploded and disabled flight control. The final explosion may have been from contact with high voltage lines or due to in-flight breakup.
1 in 10,000 chances that it’s any kind of individual target from either deep state or Iranian files, I think this is more likely to be a mistake or a terrorist act, but either of those could be used in that unlikely scenario anyway (what other ways would they have to bring down the plane, other than terrorism or missile strike? possibly deliberate faulty maintenance).
I don’t think the “engine failure” thing will hold up, it is being met with skepticism from less political people on the pilot’s forum Pprune.
Iran is broke. It makes sense they don’t have money to do a lot of training on mobile launchers.