In my corporate era, I was head of budgets for corporation that built part of the Alaska pipeline.
The VP in charge of that project, later division general manager, had a management philosophy:
"What are we doing, why are we doing it, and when are we going to stop?"
In that same era, tools like "Zero Based Budgeting" became popular.
When the chips are down, few manager have the balls necessary to truly make zero based work.
Trump is probably the closest to such an individual that will be seen in my lifetime.
Zero based budgeting requires a detailed and thorough bottom up procedure, with total support from the very top.
In our corporate case, some departments just got put out of business. VPs early retired, others reassigned if they performed a necessary function.
My own method to determine how far to cut, is until necessary tasks are not done. You can tell at that point the cut was a little too far.