You know when you play 10 mans with your friends, you don't exactly tryhard like you do in ranked 5 stack. You do braindead stuff you normally wouldn't do thinking "he's never gonna expect this" and just having fun.
But that doesn't mean you're purposefully trying to lose either. So when push comes to shove you actually tryhard for that one moment?
Yeah, that's exactly what's happening here. 100 thieves is so dogshit. Their winning rounds are only happening because of mechanics. Everything else about them is dogshit. And I'm sure Riot isn't behind this. More like higher ups from both the orgs. They told them to "try" make it a nail-biting game. And Riot doesn't mind cause more viewership this way.