This. The demoscene was young people (mostly teenagers or early 20s) doing really cool stuff with computers, trying to out-do others. It was about art, international (friendly) competition with the demo parties around Europe, and doing cool shit. It was a mix of coding, graphics, and music - there wasn't a profit motive, although many people found employment (or started companies) in related industries afterwards.

How a lot of the coding part was so hardcore is probably explained by not having things like Unity or Unreal back then, so everything had to be done from scratch