If the admin key of the smart contract is leaked, all the funds and operation of smartcontract will be at great risk. There has been many incidents where hacker compromised admin key of contract and gained the full control of it. Millions of Dollars has been lost in past due to admin private key leak.
DeFi protocol should use a hardware wallet or a multisig wallet which is considered more secure
https://medium.com/@quillaudits/wintermutes-160m-exploit-analysis-quillaudits-f1dbd217b9f9