They erased the world records when they changed the weight classes and tweaked the rules slightly. Once some time between 1994 and 1996 and again some time between 1996 and 2000. I think it was a bit stupid, but no one was really getting close to the clean and jerk world records because of stricter drug testing. Varbanov did 215.5kg clean and jerk at 75kg, Dimas never managed better than 215kg weighing 85kg. Snatch has stayed much the same though due to improvements in technique.