Sentence Correction

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?

awesomeusername wrote: 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.

First, how true a statement is this!!!! Long live U2.. Hope they go on forever

With respect to the sentence, I think the word HAD here is not part of the formula HAD + Past Participle.
HAD is being used as a verb form over here.
Eg, He had his revenge.
If I need to indicate that this happened in the past, I would say
He HAD had his revenge.

Does this make sense?? I may be wrong though!!

@awesomeusername: I have the same doubt. Did you get a satisfactory explanation for this..