What the hell even is comp

Today I did my open queue combo placements with my friend who is low diamond. I placed 10 SR away from diamond so I said “hell yeah let’s play one more game” and so in that game there was someone who was botting we reported them of course and even got the feedback screen saying they were pentalized. So why did I have to lose SIXTY 60 heccing SR when someone was literally winning bc they were cheating. How is that even fair? I don’t even know why I had lost so much SR I had maybe 4 deaths and over 25k healing which was gold and best in the match :confused: this isn’t right.