short and simple explanation
account was hacked from when i gave it to who was a friend because they wanted to do something for me. well they didnt screw me over then but as it turned out they'd got some backup codes. so at some point when i was offline they logged in, deleted all friends and were on csgo. i check my steam app on mobile and see it says im playing csgo. i know i didnt leave my pc on as i hadnt used it for the past day, so i kicked all devices logged into my account off. i got home later to see that now im game banned in csgo. i look in my demos and there you go, blatant cheating. believe it or not idc i still hate u