First, I would argue that your statement is not true that successful people always or even generally or on the average know how to be successful. But even if it is true, because they are good at one thing (starting businesses) does not mean they have anything valuable to say, or that they can say it in a way that transfers value to others, or that they are good at anything else, really.

Anyway, you're attacking a premise I didn't put forward - I didn't say his advice was not valuable, I said I feel that way when presented with articles like these by wildly successful people.