When I have ridden in the front, they have moved the control, but it stayed at a particular speed without their hand on it. Then they would put their hand back on and move it to change speed. So if it was going on the straightaway from Epcot, and something happened to the driver, it may not have slowed down. I would have thought the automatic systems would have overridden it though - and I'm surprised it didn't. A big clue will be what the other passengers say about the ride, and whether the monorail slowed at all making that turn toward the TTC. I think that will be the biggest change - I bet they really beef up the automatic safety systems.
My thoughts and prayers go to the family of the CM, and to the families who were on the monorail at the time.