Critical Reasoning (CR) | In 1563, in Florence's Palazzo Vecchio, Giorgio Vasari built in front

HiGMATNinja /JonShukhrat , would really appreciate the help on this one !

In the following question we see the following lines -> Historians believe that Leonardo da Vinci hadpainted , but left unfinished, a mural on the original wall; some historians had alsobelieved that by 1563 the mural had been destroyed.

Could you please clarify the use of past perfect tense (had painted & had believed )here ?(since i thought past perfect tense is used when we need clarity on 2 past actions or it
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