The altitude reached in the graph suggests that the engine failure may have occurred after the after take-off checks were commenced, one of which (on the turboprop I fly) is to turn off the autofeather (is it the same on the ATR?). After that the prop will windmill, and when instructing in the sim I occasionally see pilots forget or mis-handle the windmilling prop. they still expect the prop to feather.
The graph suggests that the pilot maintained the best speed he could to avoid the stall after the failure. In the final moments he was left with no option but to pull the control column aft to avoid the buildings / bridge and reach the river. The 'g' and speed reduction from this action likely caused a stall and Vmca at the same time.
We do exercises in Vmca in the sim on initial courses. We set up the conditions under which the aircraft Vmca speed is certified; MAOM, aft CG, critical engine failure, take-off flap, gear up, 5,000ft PA. If a gentle descent is maintained for demonstration purposes to allow a slow speed reduction towards Vmca then it can be docile maneuver, but the real world is never like that. If the pilot concentrates on maintaining altitude during the exercise then at Vmca the aircraft will roll very rapidly to the failed engine.
Vmca is generally close to the stall speed. Maintaining aft control column and max rudder deflection at this speed has a name: Full pro-spin action.