PSA: For those that want to try out a build that other pro players use....
There's nothing wrong with trying something different once in a while. Like, for example, an item build that one popular player uses. If you see another player's 'unusual' build bring them a high win rate, dont just copy it and think "Oh boy time for the freelo!" Find out why the player decided to use his out-of--place build and understand the requirements needed to actually pull it off successfully.
P.S If anyone can explain to me what's so good about this build for Kennen, that would be super.

From what I see, it looks like it's purpose is for fighting against tanks, but I have no clue.