Cleanup of 5th wheel accident in California

I am thinking that in most situations two seconds should have been plenty of time to stop from 40mph. I am wondering if his trailer brakes were working properly. I notice that the trailer looks to be very new. I recently bought a heavy trailer and found the brakes to be nearly useless as I left the lot. I eventually found out that the brakes need to be burnished in. I wonder how many 5th wheel campers get their brakes burnished in before hitting the open road. How many owners are even aware that it needs to be done?