If they were running a checklist trying to get some event back under control, it is conceivable they unplugged certain specific systems. If they were disabled during the time they were working through the checklist, this could explain specific systems left offline, and other systems left online.
Perhaps a 777 pilot could comment here, but it would seem the throttle, control surfaces, and flight management computer would be the last things they’d take off line —— like end of the list. It’s hard to fly and work a problem simultaneously, even when you are trained to the hilt for the situation. If the control surfaces and engines seems to be running, why unplug them unless it’s the last thing on the list?
And then there is the randomness of electrical fires. Many times some circuits get destroyed unexpectedly, and then certain other circuits continue soldiering on. There are a lot of factors related to this... inconceivable to me, who has no experience in a cockpit or simulator or flight school, whatsoever, in a plane, as to what kind of interactions crop up. However, I do understand systemology on an instinctive level... the idea that faults in systems apparently unrelated can sum to having a unexpected emergent behavior. It happens all the time in complex software systems interacting with complex hardware.
This is also the reason that just about every system on a aircraft has a circuit breaker a pilot can flip in an emergency. They may be deep or shallow in a checklist, but there has to be a knob to control every device which can generate or dissipate or transmit electric power, because one specific apparently unrelated & minor system could be causing a problem with a very important system or function in ways not apparent to anyone but the engineers who designed the aircraft. Maybe even beyond their understanding as well, which is how flaws in a system are sometimes discovered several years after a system has been in real word use.
It continued to fly for seven hours with all of these critical systems failing. That’s pretty robust design. The Swiss Air, I think it was a MD-11, that crashed near Halifax Nova Scotia was on fire. It only lasted a few minutes before it crashed. Entertainment system overheated I think.