Ok, the single AOA gauge failed.
MCAS behaved as designed, including winding-in 2.5 units at a time rather than the 0.6 ‘sold’ to the regulator.
Contrary to CFR25.671, the failure of a flight control system was not manifested to the crews via a warning system. (Arguable whether MCAS is an FCS but since it unilaterally shifts a big flight control surface to get its job done......)
The crews did not disable MCAS by using the pedestal switches.
The MCAS system was designed to utilise a single data source, there was not warning system to alert regarding a failure of the system and there was only one failure mitigation put in place (pilots).
Not exactly cutting-edge system design.