He's foolish if he left one source of income for another when he could literally have both of them together and have no problems at all. In fact, it would have been even better for him to keep doing his usual business and then use the money he earned from that business to make investments in Bitcoin when the time is right, or even do DCA, in which he wouldn't need the market to get down before he could make a purchase. I would never leave my main source of income only because one of my investments has started to work out, but I would be happy that now I would have two sources of income, and that's what most people strive for these days.

You mentioned that he progressed fast, which means that he probaby invested by the end of the bear market, and the bull run started soon after that, which made him good profit for his investments, but he lacks experience, and knowledge too, probably, and he should have at least spent some time in the market before making that decision, and I'm pretty sure he would carry on with his business along with his Bitcoin investments once he had learned that Bitcoin and the market works in a cyclical pattern, and he might have months or even years without any profit only as an investor.