Experts in the field might not have much time to make and promote a youtube channel, because they are busy writing these books and papers.
Books have been around for thousands of years, websites like YouTube for just over a decade.
I don't see the argument line here. Because books have been around for thousands of years we have perfected the creation of books (at least compared to videos)? In terms of raw quantities I suppose most books written in 2018 and most videos produced in 2019 were rubbish
care to share that intuition? this doesn't seem obvious to me unfortunately