To clarify, I understand ABBA is very popular. But I think of it as dance music. I wouldn't expect dance music to be fodder for a musical. I was referring to the nature of the music, not it's popularity.
Some of the songs were written as "dance music" from the era. Most were not, however. I don't know what you consider "dance music", however. The specifically did write some disco tracks, but their standard pop tunes aren't "dance music". But I see no reason to exclude "dance music" as material for a musical, especially if the lyrics can still be utilized in the story. Super Trouper is the only song in Mamma Mia that exists as a "performance" where the lyrics exist outside the framework of the narrative.
There was no internet in 1955? That's a shocking revelation...
Who knew that there were fewer original scores on Broadway because of the internet? Another revelation.
Did the comma trip you up? That's a creatively selective takeaway. I thought you might be smart enough to understand what I was saying. ¯\_(?)_/¯ So I guess my response to you should have been:
Just for a bit of perspective: in the past 10 seasons, we've had an average of about 6 shows per season with entirely new scores; by comparison, in the 10 years between 1956-1965, there was an average of 12 new scores per season.
Things are different in 2017 than they were 50 years ago? That's a shocking revelation...
Who knew that musicals on Broadway would change in 50-60 years? Another shocking revelation.
Next, you're going to tell us some nonsense that the musicals of 1906-1915 were somehow different than they were from 1956-1965! CRAZY TALK!
It's not as if the perspective you provided was exactly eye-opening other than as a dry factoid devoid of context.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian