Asians, dude. I guess, if you do something for years, you become pretty good at it.
I was training in the same gym as a guy, who had national BP record in his weight class and he was somewhere around 70 kilos, not sure exactly. He could bench 150/155 kilos, if I remember correctly. Dude literally just spent his days developing his bench. Triceps, pull-ups and bench. He had pretty big arms for his frame. I never saw him doing squats or DLs. He didn't seem to be undeveloped tho, he had good gains. Maybe he ate something not so legal, because there wasn't doping control, but noone knows that. He used to be pretty skinny and then, in a few year span, he became a big guy. His lifts haven't gotten any bigger tho, maybe he gave up on lifting or just stopped taking supplements.
As for bench gainz while eating clean, I've gone from 50 kilo bench and 70 kilo bodyweight to 110 kg bench and 85 kg bodyweight, doing bench once a week and mostly just developing overall strength. It takes a while. Took me 4.5 years.