Yes, kayaking like a boat. "Why does kayaking require a camera?" It doesn't, unless you want to post pictures and videos of yourself kayaking on the internet.

One can kayak as a hobby, or one can run a youtube channel about kayaking as a hobby. In which case one is no longer kayaking as a hobby, one is running a small entertainment business about kayaking as hobby.

I think what they mean is that to "Kayak on the internet" is to post yourself evidence of Kayaking on the internet. Such things would require a camera (if you want a good visual component) to show off your Kayaking adventures

They're talking about broadcasting/performing the hobby on social media, as many social media-native hobbyists do.