Exactly this. If I have 100,000 followers on YT for my software related content, why wouldn't I use that platform to post my content? Some people are also visual more visual learners and while straight text is helpful, having a trusted source going screen by screen/prompt by prompt and comparing to their machine is helpful.
So it's both content and communication preferences. HN is a self-selecting group of a certain type, but not everyone on the planet thinks like the average HN dude
Just yesterday there was a post to one of Geerling's pages where he posts the transcript to a video he's made. He could have just made a text blog and not spent the extra effort of making a video, but that's not what he does. Instead, he went the extra step to make the content available in text only. He could have just as easily left it as video only. (yes yes, creating a text only transcript of video in today's world is trivial, but an extra step nonetheless as it still needs to be added to his CMS to make the webpage)
So it's both content and communication preferences. HN is a self-selecting group of a certain type, but not everyone on the planet thinks like the average HN dude