In MGMAT SC 3rd edition, this sentence is presented:

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.

From what I understand, HAD + past participle indicates an event that happened at an earlier time than another past event. If U2's eclipsing other bands happened AFTER the group's inception in the early 80's, then how can we justify the use of HAD here?