The same way Stock Market works. Really, Debt benefits a tiny fraction of people involved in the market.
Different mechanics, but stripping everything away, roughly the same.
With Usury/Debt you pay for lending money and you pay whatever the enterprise makes money or not.
Companies also often prefer debt because it doesn't dilute shareholders which issuing new shares would do.
While we are here, please also consider that Protection Rackets also provides similar benefits!
Those slaves being raped must be so comforted by knowing that Islam forbids cash loans at reasonable interest rates.
Is Usury some kind of religious values for you?