> There are also lot of experts (obviously its the internet so anyone could be anyone) who post educational content on their field of expertise in the 20min - 1 hour length video format. I don't see that type of content anywhere else.

Exactly. This is the kind of content that I love to watch (in particular also lecture recordings from top experts).

In my observation, this kind of content is hard to monetize by showing ads: I notice that the ads shown at such videos (for me and friends - which may be a biased sample) simply neither fits my interests nor the subject area of such videos.

Imagine watching a dev talk and get a very loud/bright/cheesy ads about some construction tool. That's the kind of stuff that makes me download those videos instead.