That's too predictable and boring, the author obv didn't want things to end easily. Plus Minyoung can't do shit there like his uncle said, he's a psychopath but he's clumsy as hell. He don't got the power to cover things up.
Cheol would eventually know or have a hunch on who killed his family and would eventually get scared of Minyoung. An abusive family suddenly dying wouldn't heal someone, it would only haunt them, that's why most people runaway and cut things off til they move on and not care.

I actually agree. But why would Minyoung tell that to his face? Did he expect some uwu response typa shit??? He should've killed them and then make it look like they accidentally died so he would stay with him bc Cheol will think Minyoung the only one he has.