Because the briefs are made of multiple plys of material. Thus making his entire meet multiply since he used it for any of the events. You can go raw squat, bench and wear multiply for deads and still have a multiply total. Donnie Thompson 3k was with a raw deadlift.
Suits suck for big guys.
Briefs only means he had a pair of briefs on ( basically a strapless suit ). Usually you go briefs + suit.
Shirt he’s got another 100+ easy once he learns it better.