They were going down a hill. It's trivial for anyone, even an inexperienced rider, to exceed 20mph on a downhill slope on a regular (non electric) bike. They also claim that the combination of disc brakes and a quick release axle is dangerous and can lead to the wheel coming off while at speed..............except the wheel didn't actually come off in this case. I feel bad for these people and their loss, but it's unlikely the fact that this was an electric bike, it had low trail, or a combination of disc brakes and a QR axle had anything to do with this. It's likely it was just the combination of an inexperienced rider, two people on one bike, and a steep hill leading to excess speeds, and would have happened on any other non-electric bike as well.