There was some math and science content made in that regime, some of it even good - but it mostly got made by publicly-funded television studios with limited airtime, and subject to the inherent constraints of having to make mass-market-friendly content. But when you have internet-based platforms that allow people starting out as hobbyist enthusiasts to broadcast to anyone who can understand English in the entire world, you can do things like actually put real, difficult equations in your videos, and still have that build a sustainable audience.

In general the state of math and science communication on the internet is way better than it was under broadcast television, and this is one of many ways that the world has steadily improved over the past few decades.