It's important to keep a few things in mind:

- When you recorded off the radio, you usually had someone talking over the beginning, end, or both (and this was by design, because the radio station knew that if you had a good copy you wouldn't listen to the radio anymore)

- Your copy was a lot worse quality than what you could otherwise buy

- You could at best distribute it to a few hundred or maybe even 1000 people if you were really well connected.

With videos on YouTube you can:

- Get an unaltered copy

- In exactly the same quality as the original

- Which you can easily redistribute to millions

It's not exactly an equal comparison. An equal comparison would be copying on VHS from analog broadcast TV. Which was also legal.