So who knew?
Well, according to an article in Air Current titled “What is the Boeing 737 Max Maneuvering Characteristics Augmentation System?, (can’t do url’s yet), there was a redesign to accommodate the larger engines – they were pushed forward and upward, the (nose only?) undercarriage was lengthens.
While these changes seemed small, there was a change in handling in that the nose would start lifting (under certain conditions) that might bamboozle a pilot;
There is also some contention as to whether the airlines were fully briefed as to the use of MCAS, re-assuring them that it is was transparent, engaging when required automatically, when the angle of attack increase to beyond a certain threshold.
So you could see how a pilot, having exceeded the threshold angle of attack (as in climbing) and seeing the nose dip with the MCAS doing its specified job, (as well as being puzzled) might take corrective action, pulling up, that actually exacerbated the stall conditions. So, with the pilot fighting the MCAS, the plane might well change attitude and cycle through changes in altitude and speed in response to the pilot’s inputs.