People want to watch good educational content, but they don't want to pay for content. They may be willing to pay for convenience, but a cable channel no longer provides that.
I do lament the fall of the history channel because the documentaries were extremely fun, not really because I'm sad about missing the information on the mongols in the nth century. Hell the dragon: a fantasy made real doc in discovery channel was a blast, not really bothered it wasn't real, if anything it was a wake up call for people that believed everything they saw on there.