Velocity of money follows the equation V = P*T/M Where P = price level; T = aggregate value of transactions per delta t and M = total nominal amount of currency in circulation.
With DeFi, you can increase T because the aggregate value of transaction per delta time increases thanks to composability of money. In the traditional system, locking up money means buying an asset where that value then becomes illiquid (like buying shares of a stock, or a bond). However in DeFi, that same asset can be tokenized and used as liquidity as a tokenized collateral. For example, I can tokenize a TSLA share and then use that as collateral in a contract where I can get a yield. I could also pair TSLA with a stablecoin as a liquidity position (1:1 TSLA/USD) and tokenize the liquidity position which can then be used in other contracts.
The total aggerate value per unit time increases thanks to composability of contracts. You should download Metamask and use DeFi, it'll become clear what I'm talking about.
You want higher velocities of money because then that value is being put to work. When you have low velocities of money it means you have hoarding behavior which leads to deflation and a shrinking economy. With DeFi, the same value is more efficient than the traditional system because that value can be allocated more efficiently (i.e. higher yields thanks to tokenized positions and composable contracts), thus you get more bang for your buck so-to-speak.
Also, just having something like Uniswap with pooled liquidity means assets are more liquid, which also increases velocity of money. More liquidity = higher velocities of money. This is how you bank the unbanked, by giving everyone access to financial markets as long as they have an internet connection.