The math? Compound interest grows exponentially (even with simple interest, usurers just re-loan), while the real economy doesn't compound in the least. Thus, ever-rising debt until serfdom snaps the masses into following a strongman. Read some history books!

You're just not seeing it yet, JAS. Economic rent is a parasite on the real economy.

If you're serious about understanding the truth about usury, read Michael Hudson's Killing the Host and Forgive Us Our Debts.