The speed was because they were rolling the pickup onto the trailer without power (probably the reason for carrying the pickup on the trailer). If all had gone to plan, they likely would have barely had the momentum to load the trailer, perhaps with some final positioning with the come-a-long.
The triangle shape of the ramps should have provided some support to the rear of the trailer, but only if there is absolutely no movement of the trailer. Wheel Chocks, Emergency Brake, having the tow rig in gear, and perhaps someone on the brakes too and they might have kept the movement to a minimum. As happened, the triangle shaped ramps kicked the ends up, had they been straight ramps, there would have been sagging, but the ends wouldn't have kicked up.
Supports on the trailer rather than the ramps would have helped, but pushing the trailer forward a foot... would one have bent the rear supports?
A good winch on either the pickup, or the trailer would have been very helpful.