Do not really have enough information but there are a number of factors that could have caused it. Do not know what a 19 rr is or your TV so can't help there either but......... My first thought is you were traveling too fast for the conditions, but again I don't have enough info. Trucks and trailers take a lot longer to stop than towing solo.
Just my 2 cents, speed, brakes, size of the tow vehicle to the trailer, brake adjustment, when you started braking, road condition, wet pavement, are just a few of the possible things that could have locked up the brakes. More than likely a combination of all of the above.
Experience is the big key......... glad nothing serious came out of it.