It's not like this is the first time elite kickboxing has been disgraced, there is a large track record of kickboxers losing in actual kickboxing against MMA fighters, football players and freakshows with no striking skills. People will rationalize it and make excuses (see Bob Sapp vs Hoost), and pretend that "elite" striking of kickboxers wasn't exposed as a joke for the Nth time.
It mostly has to do with the depth of K-1 HW division. This isn't the first time a big brute with limited skill has looked great in K-1. And yes, Overeem didn't win a GP mainly with his skills, nor do I think his skillset is world class as everyone thinks he is
This says absolutely nothing about kickboxing. Seriously, who gives a fuck? I was personally pulling for the Reem, but a good win for Bigfoot. That's all that needs to be said.