Sentence Correction

Good day
in the Manhattan SC book, page I've come across the following example

Right: The band U2 WAS just one of many new groups on the rock music scene
in the early 1980's, but less than ten years later, U2 HAD fully ECLIPSED
its early rivals in the pantheon of popular music.

What puzelled me was that : the action "was" was previous to the action "elipsed" and despite that we used past perfect for the last action and simple past for the former action

Any explanation???
Thanks a in advance

It's kind of a weird one. First, we have two different time frames: the early 80's, and less than 10 years later (so the late 80's?)

In the early 80's, U2 was one of the new bands. Okay, that's fine.

Less than 10 years later, U2 had eclipsed those bands. The past perfect is used here to express that the action took place before the point in time "10 years later".

Thanks Bill, it's clear now!!!

I'm glad It's definitely a strange one, and on the GMAT past perfect will nearly always be followed by simple past.