1. when mtv first launched, explain how the station got enough content to fill 24 hours of music television.

When MTV first launched in 1981, record companies and bands had remained making music videos for 20 years or so but they weren't known as music videos. No one had thought before MTV to put these videos together and play them successively and repeatedly.

When MTV firs aired in 1981, the many record companies and bands were already making music videos. They have been doing so for 20 years already. It seems that, before MTV, nobody thought about putting those together and airing them continuously and repeatedly. That's what MTV did.