Yikes. Rookie RVers can get into serious trouble. He's lucky he didn't kill multiple people, much less do damage to his quarter-million dollars of truck and trailer.
His problem wasn't the GVWR or even the overloaded tongue weight, his problem was not using a proper weight distribution hitch with anti-sway control. And also, not knowing to tap the brake controller for the trailer to reduce sway, while keeping your foot OFF the truck's brake.