As a mid lane main, my win condition right now in every game is to play a hard wave pushing champion, go botlane and double kill. It doesn't matter who gets the kill, but putting the enemy bot lane behind is essentially GG. A small advantage to a bot lane can change the landscape of the entire game. I also save my bot lane from inting by helping them in their lane which can also lead to a huge game loss.
I could smash my lane opponent into the dirt, but if my botlane loses priority and/or advantage then the other bot lane can really tear through the game. Certain mid laners can 1v9 don't get me wrong, but I feel like a winning bot lane is the best way to win the game right now.