What actually triggered Bernard to take the actions he does at the start of S1?

Note: I've read Wool but I don't believe it provides any further info to answer the question, so I just went with a show-only flair.

What actually triggered Bernard to effectively take over Silo 18? We know that for at least 3 years (likely much longer) he was happy to control IT/Judicial whilst leaving the Mayoral and Sheriff departments as separate "branches".

When Holsten asks to go out, he immediately attempts to grab power of all 3 "branches". Did he always want this and just saw the sheriff going out as an opportunity for this? Was it a panicked response because a sheriff had never been sent to clean before? Or perhaps it was a command from the Order or his yet-to-be-revealed overlord(s) (the "who" he mentions in S2E10)?

Thoughts?