Williams is a cartoon character. Bottom line. And Justin Kestleman loves him - ergo, daddy decides that if his boy loves something, he's going to get it for him. Fundamentally, that's why he has a gig in the first place (actually Justin is the fundamental reason LK bought the NBL, but that's another story).
As a colour commentator in the traditional sense, Williams is absolutely horrible. Does zero research, doesn't analyse the game in any coherent fashion and is really just a mouthpiece for himself. If anything, he talks down the league and certain players way too much. Doesn't say much for your product when one of your callers is bagging it to the extent that he does.
But again, this is all about the NBL and their broadcast strategy. If nothing else, Williams does generate discourse - this thread a prime example. The league (i.e. the Kestelmans) believes that because so many are talking about Williams on social media and the like, that will translate to higher TV ratings, which ultimately (they hope) leads to an actual broadcast deal - that is, one where some actual money is flowing to the clubs rather than the unsustainability of LK paying for everything, which is the case right now. Time will tell whether they are right or not about that.