e.g. you like to play a lot of chess. So you COULD theoretically monetize it by making content about chess (youtube, ebooks etc.), maybe even do some events but still.. that's not the same as playing chess which is what is your hobby is about. Thus, making money with your hobby would then indeed not relate (much) to the actually fun part about the hobby. (although you can argue that working as a writer on your hobby is better than being a writer about something you're not that interested about. However, it might sour your hobby.)
Making a positive income on youtube is incredibly difficult. The competition is very high, the pay is pretty subpar, and the hours are long. You also need to take a few (yes, a few, not a couple) years off of your day job to work entirely on content and marketing to get your channel off the ground.
A topic like chess might take 60 hours a week of video editing over the course of years just to get to 4k/month in income IF you beat the nearest 10,000 competitors who are trying to make similar channels.
