For all those questions about WHY this MCAS on B737 MAX fleet, the following link has a very nice easy to follow explanation with clear graphics written by a test pilot Bjorn Fehrm.
When you apply a lot of lipstick to an old lady like B737, something else goes wrong. Boeing had to do this change as the large engines made the aircraft stability to go wrong. Thanks Bjorn. I think it will clear up several questions about MCAS, STS, etc. in this forum.
https://leehamnews.com/2018/11/14/bo...to-the-pilots/