I agree that their poor judgement is mind-blowing but I think this Guardian piece holds some clues:
https://www.theguardian.com/politics/2025/sep/10/my-best-pal-messages-between-mandelson-and-epstein-suggest-a-close-bond
Staley allegedly sought Epstein’s help to meet Mandy as presumably they could, allegedly, be useful to one another, with the result that they might both feel beholden to Epstein for the introductions? And Epstein used his Manhattan residence to facilitate all of this?
Apparently Epstein, astute networker extraordinaire, used to host dozens of completely legitimate salon-type dinners on a regular basis in NY where industrialists, bankers, scientists, senior politicians and celebrities would all mingle; similar to the above, with the upshot that a lot of influential people ended up feeling grateful to Jeffrey.
And these events, which gave no hint of Jeffrey’s darker side involving the sexual abuse of trafficked minors, gained him a certain legitimacy among the elite.
Epstein appears to have operated just as Saville did, by hiding in plain sight, and mixing legitimate work and above board social networking with nefarious and criminal activities, duping many influential people, and using friendships in exalted circles to his own advantage, gaining legitimacy second and third hand.
Mandy I think, if you look at the history of his previous resignations, has always had a weakness over money or being impressed by wealth eg Geoffrey Robinson and the Hindaju debacles. And you can imagine him alone in NY as deputy PM thinking he might make more “interesting” contacts staying at Jeffrey’s and all the better if he gets to keep his £400 nightly government stipend or whatever was allocated for hotel accommodation? He presumably never imagined that any of it would become the subject of public scrutiny sixteen years later?