This is actually the key one - the more people who need to be corrupt, the harder it is to get away with being a crook. A surprising amount of internal fraud can be completed simply by requiring people to take solid blocks (2 weeks plus) of leave every year.
That "inefficiency" the "lean 10x disruptors" congratulate themselves over does not always end well.
I've heard that's because a lot of those scams/tricks fall apart without constant gradual intervention, so an important part of it is that the employee is prevented from accessing most work-resources during that time.
But at a job where the ideal is automation, rather than manual verification and analysis, I wonder what additional obstacles must be placed in a potential attacker's way? Rotating keys based on employee schedules? I'm sure there are many well-studied ways to do this, but it's interesting to armchair analyze.