The Max planes are misleadingly called 737s when in fact they are a major re-design. The wings had to be shifted forward to accommodate the new engines so it handles differently.
The change in wing position plus the heavier engines apparently gives the nose a tendency to tip up at times, so they decided to add this ‘MCAS’ software to ‘help’ the pilots.
But they didn’t tell the pilots that the MCAS was there, and they obviously didn’t limit it only to times when the plane has a lot of altitude, and worst of all they didn’t give the pilots a way to turn the damned thing off when they rotate off.
That’s sort of what I’d gathered. They put software in place to smooth out the minor aerodynamic anomalies. But software itself is inherently prone to unanticipated bugs, as every programmer should know. It undergoes a lot of testing and then still surprises everyone since unlike humans, it can’t think beyond what it’s been told. It shouldn’t be used at all to compensate for a plane’s bad handling.