sorry but i offer you the well known counterexample of the assassination while in LE custody of lee harvey oswald as an example that law enforcement should definitely never seek to follow, even passively.
Standing down can mean a lot of different things.
They could have done due diligence to make sure everything was done by the book, that Epstein was protected, etc. At the same time, it’s clear they avoided taking any extraordinary measures to ensure it didn’t happen.
My perspective is that they figured out a way to turn this potential negative into a positive ahead time.
Isn’t that struggle in every surveillance or undercover activity taken on by the police? How much evil do you let go unpunished to ensure you take out the whole system?