Articles like this are missing the overall context. People don't turn hobbies into side hustles because their day job is so fulfilling or they earn more than enough money from it, or because they are generally happy about their position in life. They do it because their job is not fulfilling or they are genuinely unhappy in it (worker dissatisfaction), they don't earn enough money from it (real wages going down over time counting for inflation), and/or they are unhappy about their position in life (looking at other people on Instagram.)
Unless the motivations to start a side hustle are explored, articles like this are a bit hollow.