How Dafuq are hecarim and kennen meta top laners.

Although, they have gotten buffs.

Kennen did get a buff to him actually. His ult now applies a stack to everyone in the ultimate and now the ultimate will hit multiple enemies faster for team fights. Honestly, even before that buff, he has always been pretty strong. People are now started to rem how good he is.

I still don't understand Hecarim in any lane. How does it work?

Kennen I can understand..I don't get how hecarim became a top laner in the meta even more so how he's been winning his matchups

The buff to kennen while it may seem small, it made him more reliable. Hecarim I have no idea.

Hecarim W was buffed in 5.1:

Next stop on our 2015 Jungle Love Train is none other than the Horselord himself, Hecarim. Jungle difficulty's been rough on our little pony, and with no spirit items to keep his sustain up, he's found more time in the stable than we'd like.

Turns out that giving him enough sustain to handle the jungle also gives him a ton of sustain in lane. Who knew?

Certainly not us -- Hecarim top was a super high win rate champion in high elo, but nobody noticed until someone tried it in LCS.