If I run a bakery and you run, say, the Mint...
Ten years ago, I bake a loaf of bread, and sell it for a dollar. Then I invent an amazing machine that can produce the same bread more cheaply. I'm about to drop my bread prices, but you mint some new coins and add them into circulation. So I keep the price at a dollar per loaf.
I scrutinize my bread supply chain to the last detail. I optimize the flour, I optimize the temperature. I fire all the workers and replace them with machines. I'm saving every penny I can. Loaves get made faster! Loaves get made cheaper! Bread is flying off the conveyor belt!
You pull a lever and crank up the printing press. Dollars are being added in the millions, in the billions!
The price of bread stays at a dollar; has the currency been debased? I honestly don't know.