braking problem

We have a 2022 Forest River Flagstaff Microlite 21FBRS travel trailer. My tow vehicle is a 2012 Chevrolet Silverado 6.2L with the max trailer package. On a recent trip, our truck brakes had a problem. Had to push all the way to the floor to stop and it took a while. And we were on a flat road. Fortunately we were close to home, so we drove slowly and carefully to our house. We disconnected the trailer. I then drove my truck for a while. The brakes worked just fine. So I concluded the problem was with the trailer. My question is why did the trailer cause my truck brakes to fail?