Information is siloed, teams compete rather than cooperate, any team's own dossier is going to be seen as biased and unobjective.
There's real value in hiring a neutral, competent vendor to come in, assemble the relevant information using best practices, and present a "dossier" with common-sense conclusions. Then the leader who hired them can use that as political cover for taking the necessary actions they wanted to in the first place, because the leader is no longer siding with one bureaucratic faction against another, but merely taking objective advice from an outsider.
That's actually worth a lot.