Fiat is latin for "let it be done". The masters of the fiat system want the power of kun faya kun, which belongs only to Allah swt. Without any effort, they press a button to virtually print money and steal value from everyone.

Riba is an attempt to create something for nothing, which is a failed attempt to replicate the 'kun faya kun' power that only belongs to Allah swt.

Of course this power cannot be manifested in the real world as there's a hidden cost associated with it. This cost is the debasement of civilization and the loss of human life.

Riba has always been the true philosopher's stone.