You didn't dominate enough. You didn't win your lane hard enough, help mid win theirs, invade the enemy jungle and steal some buffs, carry team fights, or pressure objectives. I know people hate to be told they aren't good at something (keep in mind I still consider myself bad at this game), but it isn't hard to completely carry a game when your personal skill level is well above the enemy teams. Just winning your lane isn't enough. You have to destroy it to the point where the enemy team has to 2 or 3v1 you as you split push your lane in to oblivion. You have to head bot after taking top turret and gank their lane with your jungle so you can pick up a double kill, another turret, and then dragon. Carrying is easy, its just having the mechanical skill and the game knowledge needed to be that much better then your current opponents. If you don't have it then either you play a shit ton of normals or you practice until you do.