I bet you are a pilot
Adding on to that...
How would the generators have closed onto the busses with that CB tripped? Since the CB in question controls those (and a large portion of the other, if not all, electrical control units) as well.
IMHO everything is pointing to a CB trip of C829, probably at the activation of the ALT GEAR extension sequence.
I suspect the final report will say the crew failed to identify the C829 as tripped and was unable to resolve that resultant issue in flight (including in discussion with MX).
Even if it tripped but not popped and was "jarred" loose during the "grind-out", as some have suggested, I would still be surprised that a basic "cycling" of the breakers was not done when dealing with an issue as severe as this.
To each their own though, I guess my "archaic" techniques learned as an engineer don't have a lot of room in the age of EICAS.