Well, I didn't really mean to say that what made him a billionaire was making it hard to cancel amazon prime, that was just an example I came up with that demonstrates Amazon general stance on user-friendliness.
Still, I'm not sure I understand what you're trying to dispute. If we agree with both premises(1. Bezos is a billionaire and 2. Amazon products aren't usually user-friendly), than I maintain my position that the expression "Jeff Bezos did not become a billionaire by being user-friendly" evaluates to true.