https://www.nytimes.com/2019/04/08/business/boeing-737-max-.html said:
As Boeing pushed its engineers to figure out how to accommodate bigger, more fuel-efficient engines, height was again an issue. Simply lengthening the landing gear to make the plane taller could have violated rules for exiting the plane in an emergency.
Instead, engineers were able to add just a few inches to the front landing gear and shift the engines farther forward on the wing. The engines fit, but the Max sat at a slightly uneven angle when parked.
While that design solved one problem, it created another. The larger size and new location of the engines gave the Max the tendency to tilt up during certain flight maneuvers, potentially to a dangerous angle.
To compensate, Boeing engineers created the automated anti-stall system, called MCAS, that pushed the jet’s nose down if it was lifting too high. The software was intended to operate in the background so that the Max flew just like its predecessor. Boeing didn’t mention the system in its training materials for the Max.