Tanks trade constantly in top lane especially the pros. So they are doing damage constantly that just gets sustained through all game and doesnt really do anything.
If you see any of the graphs after team fights they are normally no where near carries. But over the coarse of the game beating on abother tank for 30 minutes they will do damage.
Maokai is strong but this graph only means their carries died too fast or couldn't get in to do damage or both.
In the game that C9 just played Jensen on ekko looked a lot more impressive than. The Maokai on the other team that lost.
If tanks were so OP there would be 2 in every game minimum. But there arent.
I guess you missed the game the other day where MF support won a team fight basically solo off of one good ult.
Also CoC is getting a nerf next patch and they are buffing lethality.
Mao is also really strong. He doesn't represent tanks as a whole.