Can someone help explain why people get caught 30+ mins into a game?

Just had 1 of the best games 5v5 i've had in a really long time. The game was super fun intense and we were just BARELY winning but nonetheless it was an interesting game with a lot of skill on both sides.

Then, 30 mins hits and its like players on my team just teleport into the middle of nowhere and die and the game ends.

Why does this happen? I was enjoying a really good game and now im just angry that we lost the way we did.. It wasnt like it came down to 1 last fight, it was just 2 players had no idea wut they were doing 30+ mins into a game and we lost.

yes im salty.. idk how to enjoy this game anymore when games end like this.