Abba have had their first ever US top ten album - although, actually, they haven't, as it's the Mamma Mia soundtrack and thus, more accurately, Meryl Streep's first top ten album.
Still, Gennaro Castaldo has something to say about it:
Searing insight. The music featured in a film is a key component of its success. Erm, especially with Mamma Mia being a musical. That might well make the music incredibly important.