Because of economic downturn in the world, most people have become jack of all trades and master of non. learning skills and not getting a mastery of them because they are testing waters on which of them will eventually pay the bills. I have a friend who during her spare time learnt soap making, baking, sewing yet she's not making money off these skills.
That friend of yours is not serious. Being a serial entrepreneur does not neccessarily symbolise that general saying "jack of all trade and master of none". One can learn different skills and still become very profitable with those skills if he plans himself very well.
Like I said previously on the post you created, a good entrepreneur will take things one after the other. Failure will arise when he tries to take up everything at once. It shows that the supposed entrepreneur does not have a real plan, I can say he is disorganised and as we know, organisation is the quality of a good entrepreneur. There are successful serial entrepreneurs, if you listen to their stories, you would learn alot about how they started.