Going to be lots of human factors focus here. Interactions between pilots, between controllers, between pilots and controllers.
Why the CA/PF was on the radio descending through 17,800' when Approach cleared them for the 26L transition (they were actually told that they "can" fly the 26L, pilot appeared to say "91" but did not read back the transition change).
What was the FO/PM working on.
Why they were approaching RDFSH at 6000' and not GARRR at 7000' (sure, Approach thought 3591 was deviating for weather, although they hadn't cleared them for it, and Approach didn't ding them for being at 6000' instead of 7000' for GARRR).
Why the constant 240KTS in the descent with the parabolic drop-off at the end, were they in speed mode, what altitude was set.
Did they have a high rate of descent result from pulling power while trying to decelerate, did the 30,000 FPM final rate of descent result from a departure from controlled flight-- maybe with parts coming off-- in the effort required ("PULL!") to bring the nose up from 18,000 FPM through 11,000 FPM, which is where the bottom fell out.
Not throwing stones here. I live in a glass house of my own making. Just looking for the most obvious/likely causal factors. Occam's Razor. Whatever you do, don't ask how I can envision this scenario happening.
I've worked through it a number of times and have a more lengthy write-up, that is, if you want some more conjecture as to what happened. Guys just out trying to make an honest living, and the whole thing went to hell on them. Whole thing makes me want to puke.