Perhaps he genuinely enjoys his job? Why should he have to launch another business? He already started one and it's very successful! Let the man enjoy his freedom and have a regular job if he so pleases!
If he liked it that much, then probably he wouldn't have started a whole side project that must have consumed evenings and weekends for years.
If he would have found professional fulfillment in his job, he would not likely have started a side project in the first place.
As he mentions in his own reply, he stays because he feels that his job defines him as a person, and he would lose his social identity if he left.
This is a surprisingly lucid reply, he can do whatever he wants and I wish him the best, but it's clear to me that he has other much better options available.
Some people have higher-dimensional desires and interests in life.
I'm saying that there are other dignified ways to live that are different, you don't absolutely have to be an employee at all costs.
Independent work, running a small business, those are other alternatives to live that are equally valid.
I understand his position completely.