Mulvaney was a Bush League mole in the Trump White House, among many others.
Half of the Executive Staff in his Admin where Establishment Shills.
Most of his secretaries too.
And some of the ones who are arguably on the MAGA side, got chased out one way or another.
Completely nonsensical fantasy. It was common knowledge that an arrangement was made with the Archivist to keep items the President deemed personal until a resolution was reached. The safe was one built into the structure by Mariweather Post, not hard to discover. Less known is that Trump never used the safe.