I read the title as "Badger leads archeologists to hoard Roman coins". From what I can tell, "scarce money" i.e. the gold standard is a pyramid scheme and it is entirely plausible that the empire expanded its borders simply to acquire more gold/silver as it is so easy to hoard and thereby take out of circulation while simultaneously being needed to pay the soldiers. The pyramid scheme stops as soon as you are unable to conquer more land that is bearing precious metals. You can no longer pay your soldiers and they might turn against you. This is especially bad if you are simultaneously being invaded and your main force is busy fighting a war.

By the way, we aren't enlightened creatures that are beyond this sort of pattern. Urban sprawl is exactly the same thing. Plots of land sit empty for speculation, which forces people to move further away from the center.