They sold a lot of records.
My guilty pleasure Abba song is "Dancing Queen" because it reminds me of my first crush on a girl. I was 14 years old and she was in my freshman Biology class. We shared a few labs together.
Fled to Monaco, IIRC to avoid paying for the Swedish Welfare State.
Turned down a billion: https://www.businessinsider.com/abbas-1-billion-reunion-offer-2014-7