It never ceases to amaze me that blockchain aficionados on one hand praise the supposedly revolutionary transparency of the blockchain, while on the other hand extolling that the "state of the art" concept of a ledger that isn't on the blockchain, is going to be what finally makes crypto "scale" and become viable for the masses.
In a similar sense, blockchains with layer 2 scaling, result in all address balances being stored in the central blockchain, while people can transact with each other directly and instantly in a zero-trust, cryptographically secure manner. When either party in the transaction is "done", one of the parties will commit the address balances to the blockchain for the world to see. (The only model that makes sense, and actually allows for scaling, is a hub-and-spoke model, where everyone connects to a "node", much like with DNS, and lets the node handle the routing. This way users could keep accounts open while transacting with many different people / businesses.)
This means that Ethereum transaction fees for DeversiFi's end-users are extremely small because they use almost no marginal L1 Ethereum gas.
So, Bitfinex subsidizing DeversiFi's users' gas fees is not as expensive as it may sound.
In this case, the $23.7M fee was likely in error and unlikely to be money laundering because the fee was paid to a random miner.
If you're interested in Ethereum's state-of-the-art scaling technologies https://starkware.co