"All the pilots had to do was flip the stab trim cutout switches and trim the aircraft manually. At the speeds they were going it would have been difficult to turn the wheels, but they didn't slow down."
With MCAS disabled, all power assistance for the stabilisation functions were also disabled. To achieve the trim adjustments, they had to execute a "roller coaster" where they dropped altitude to reduce the air pressure over the control surfaces and reduce the required force.
At low altitude.
In a plane that was not reacting how they expected.