I know about the Roman empire, and you're right, it got itself killed due to hyperinflation
However, you fail to address the underlying reason: The whole roman economy was built on slave labor. And when they stopped conquering, they stopped getting the new slaves to run the economy. That's what killed the economy, which resulted in the hyperinflation - not an MMT style monetary expansion. That was just the result of the economy failing - similar to what happened to Germany after WW1, who got crippled economically by the Versailles treaty.
I don't think it has anything to do with slavery, which, on the contrary, would be a cause for potential social unrest if it were too large of a percentage of the popuation. It had been over 300 years without conquests when the Roman Empire fell, perhaps because they did not do something the Persians used to do: periodic raids in "barbarian" lands to keep them in check. Roman Emperor Majorian and later the Arabs, in the Iberian peninsula, showed just how frail the germanic kingdoms were against a minimally organized force. The Chinese comitted the same mistake, more than once, but Eastern Asia geographically favored the reassembly of a monolithic empire in a way Europe didn't.
OT - can we focus on the main six or so candidates already, and have the filler ones drop out? No one has ever surged from below 5% (and that's being generous, since it's more like 8-10%) in the primaries polls to win this late, 16 months before the election. At post you have types like Kasich and O'Malley who decide to stubbornly hang on far beyond any hope (though, to be fair, a lot of protest votes were dumped on Kasich).