If $MKR is a decentralized then how are decisions about fees, pe

The system is meant to be governed in part by a governance token called MKR that allows holders to both make decisions about the system as well as act as a lever to stabilize the DAI price.
Conversely, if MKR token holders govern the system badly so that CDPs do not have enough collateral, new MKR tokens are automatically created and sold, bringing the system back to sustainable levels, but also effectively decreasing the price of MKR.
DAI’s remarkable resilience is due to the system of collateral and lending at the heart of the system.
#DAISupply MKR
mkr.tools/tokens/dai

Collateralized Debt Positions (CDPs)
Loans are created and new DAI issued through what are known as Collateralized Debt Positions or CDPs.
blokt.com/guides/ethereum-guides/ethereum-lending