Bottom line... using Mitnick in this way, especially adding him to the board... is KnowBe4's way of telling me how they view themselves. It's their warning, in a way. A way of expressing who their target audience is.
Just like 🌶 did with him. They knew that their primary audience wasn't IT pros, but buyers looking for big names and flashy acts on stage rather than technical know how and expertise. That both of them use Mitnick in the same way is very telling.