Not saying you are right or wrong, but from my perspective your bot lane obviously lost their lane. I'm thinking their turret was gone in first 17 minutes at least! i dont know who your jungler was, but if they lost their turret they obviously or shouldn't have stayed in lane (unless enemy pushed it of course) so therefore they started to group mid/roam. You going 9/4 is good n all, but im guessing you literally stayed in lane and farmed and rarely came to team fights because you are nasus and getting "stacks" like a lot of people who play nasus do.
You should have been able to carry at this point. A. You should have had so much pressure in your lane by pressuring turrets, that the enemy team couldn't ignore which allowed your team to put pressure elsewhere, or you should have pretty much dominated team fights, because you sound like you should have been most fed person in the game.
So it definitely wasn't your fault you lost the game, but it was partially your fault. There is always something more or different you could have done.