I think they do investigate. They probably turn away the obvious corrupt scams, and that sort of thing. And there is a small amount of up front assistance to the creator. I agree though KS is responsible, and should do a better job to maintain a higher success rate.
There are other crowdfunders that do a much better job. As for instance Crowd Supply from Mouser. They talk about a 100% success rate,. Don’t know if that is still true. They do electronic musical products too.