IIRC, deflation mostly occurs when companies overproduce in a bad economy. Basically when there’s a surplus of goods and companies can’t get rid of them.
Deflation is generally considered bad because it becomes harder to pay off debt. IOW, your debt level increases due to interest faster than you can pay it off.
wevets - I don’t believe money is considered a commodity because it comes from a single supplier - the government and US banks.
As opposed to say, oil or gold which is the same product regardless of who supplies it.