He removed money from Uniswap. Uniswap is a decentralized exchange. At the heart of it there is the ability to provide liquidity by funding the exchange wallets.
Imagine Dollar and Apples as our currencies. The exchange rate is 1 to 1 for this example. So in order to provide Uniswap with liquidity you give them 100 dollar and 100 apples. People can trade against those assets, in turn you get a small fee for every trade. If person A comes along and buys 40 Apples, the Uniswap wallet now contains 140 dollar and 60 apples. These still belong to you, as they represent your share in the wallets.
What Techlead did is, he created a coin (like our Apples) and provided Uniswap with his coin and USDC (basically a coin tied to the dollar). This way people could buy his coin. No, after them buying he pulled out money from the wallets, now his shares are predominantly in USDC. By removing the liquidity the pools are now incapable to provide sellers of his coin with USDC, therefor the market is dead.