It wasn’t crashed, it was landed.
Look at the videos from Iran. Crashed birds don’t survive so intact.
Most likely China or Russia were involved in gaining control of the avionics. There may have been irratic control issues explaining the dent in the leading edge on the left wing, about a 3”-6” dent, maybe 1-2” deep, but quite truthfully that also could have been caused in transporting it while in enemy possession.
Some bloggers already are suggesting the problem was crypto being leaked over to China and the Chinese taking control of the aircraft, which makes more sense than it ‘crashing’.
I see no evidence of it being ‘shot down’.
http://essential-intelligence-network.blogspot.com/2011/12/rq-170-anatomy-of-failed-cybernetic.html