The first MCAS event (and perhaps the only one), seems to have occurred just after the aircraft left the ground.
For the Lion Air accident flight, the captain's stick shaker activated whilst the aircraft was still on the runway and continued for almost the entirety of the flight. If this was the case here too, then the apparent pitching down and early reports of "flight control problem" may have been the pilot responding to the stick shaker.
The question is; Was the flap raised instead of the gear after rotate, thus activating the MCAS?
If I was a betting man, I would bet my house that this wasn't the case - purely because the odds against having both these events at the same time would be astronomical.