We also have better market research today. Star Trek could have flopped and nobody would have noticed. Many scifi series did. Today's production companies have vast research departments who are actually very good at predicting outcomes. The risk is less, so funding for established organizations is easier and margins are smaller ... the basic economics of a mature industry.

As I said in another comment below, I would argue that funding TV shows today is the bad idea. Those producing them still earn lots of money for them and their friends. Production is still very lucrative. I just would not want to be an outsider investor.