Do what? Bum tried to poison Sangwoo and planned escape several times. Sangwoo, differently from this one, was actually dangerous and unpredictable.
Bum did it for survival after taking so much mental&physical damage by sangwoo. He wasn't as courageous as this guy lol he only tried to save himself a few times because he had to. Besides it took him way too long since he was still in love
In this situation the mc also admires the ml but not to the point of being a stalker or having stockholm syndrome (like bum). He doesn't seem to want kindness or non-physical love from the ml yet, so he just does whatever he wants without feeling mortified by the ml. Whilst in bum's situation everything was on the line, cuz bum knows once sangwoo sees bum doing something even slightly irritating, sangwoo will go crazy and bum was scared to be hated by sangwoo :D
Hope i could get my point through, my first language isn't english and im in a rush to attend my online class lol
*get my point across
Come on guys this is nothing like KS :D Bum never had the guts to do this