Some content costs money, other content - and how I dislike the word 'content' which turns that which makes the 'net interesting inside-out to make it into a money-making scheme - costs time to make. Not all time is money, lots of it is time spent on activities which people do without the need for payment since they enjoy it. Call it a 'hobby' or 'pastime' if you want, something to do when you're free to do what you want. Some people like to go and watch sports games, others like to sit on the sofa and watch televised drivel while others park themselves in front of a computer to create something. Much of what is created is interesting only to the creator for the act of creation but some of it has value beyond the experience of the creator. That is indeed how the Linux kernel got started, it is how a lot of music is made, artwork is created and more.
Maybe not an entire industry, but Bellingcat has been impactful and it started with a guy commenting on the guardian comments section.
Content costs money to make. Yes, sometimes give via self-funding of the content (without advertisement, like by working a job), and that's fantastic. But we also need a way to support the content that we like, and we can't expect everyone to be able to give.