I hope this is right place to put it, but why is Abba getting more attention then the Thank you project?

My theories include:

Most obviously it's been 40 years since ABBA has released new music while Diana Ross was pretty busy with new music between 81 and 99. And though there hasn't been much since Every Day is a New Day, she has toured [[especially in the US) and occasionally does TV and interviews and award show appearances.

But I also think that whoever has managed the ABBA brand the last 40 years has done a remarkable job keeping ABBA known. Through releases of Greatest Hits projects, savvy marketing such as Mamma Mia theater show and movies, as well as licensing hits for movies and TV which allowed for new generations to discover and like ABBA.

Also helps that all of ABBA's songs/hits were written by Benny and Bjorn so I suspect they have some control over their catalogues, whereas Ross only wrote a handful of her songs and her back catalog is spread out over Motown/Universal and RCA/EMI. So that makes it difficult for her to control the legacy.

Other reasons?