That lock nut may not have lined up correctly for some reason and was backed off a bit to get the pin in? That could make it torqued under spec. But also, it doesn't look like that bolt clamps anything so it may not matter if it was a little "loose"..
Are you looking at the center nut in the photo that's cotter pinned in place, or the two over on the right side that appear to be "loosely threaded on at best, washer rattling along the shaft"?
The center one doesn't concern me. The two that aren't even finger tight do.
I was and missed everyone was talking about those other bolts in this particular case.
Those are much more problematic as the remaining tight bolts could fail leading to a cascade. Though, would expect the flange to still be connected to the post in the aftermath images and the upper pins .. how did they get out of the track?
I wish we had close up pics of all the bits in the airframe opening.
Complicates the issue of who is at fault; where/when were they loosened?