Luna is a good example on why we should not trust new smart contract code even if audited. The algorithmic part was the problem here in my opinion and how it got exploited using a lot of money.
There's no problem with the smartcontract code but the mechanism of algorithmic stable was the main concern in this case. when UST gets burn and more Luna minted from the contract but the worst thing is when more and more USDT burned and the inflation rate to minting luna was so high and this is triggering people to convert their UST into the luna.
I remember at that time so many people are also burning their UST for luna. These people were dumping their luna from the contract to the market as the price is still so high.
When people burn UST and they will be getting $1 worth of luna. This is triggering the massive sell happening with luna.