I've said it on page 4 and I'll say it again:-
Normal electrical power appears to have been working as the transponder and associated ADSB was on
No emergency 7700 set
No Mayday call
374 kts GS at impact suggests around 330 Kts IAS
3,500 fpm descent indicates an open descent with speedbrakes.
So, a decompression event occurred at FL380, the crew started the Aircraft down but then somehow ( Oxy system failed, injured etc ) became incapacitated and the Aircraft continued until it flew into the ground.