Try to imagine being a low altitude and not knowing how to manually trim the airplane. If either of these crews had been able to do that, the airplanes would still have been flyable.
They had the ability to correct the trim--but some pilots method of trimming an airplane is to turn on the autopilot. As far out of whack that the MCAS seems to put the trim, the autopilot would not be able to turn on--or not have authority to keep the airplane in level flight.
TTFA -- if you're a pilot and don't know that acronym, you're part of the problem.