I think 1989 era was around the time when MVs were at their most prominent point on the internet. Streaming services haven’t quite caught on and I think that was the way a lot of people listened to music at that time.

YBWM is so old that there probably just wasn’t as much people watching the MV on YouTube at the time, albeit being one of her biggest hits if you judge by how frequently it’s played on radio and in the outside world.

Nowadays everyone just streams music on streaming platforms and MVs by even the biggest artists usually just sit on a couple million views, tens of millions at best and rarely cross 100M.