Correct me if my understanding is wrong, but there are no crypto transactions involved with arbitrage in the common case. Arbitrage is concerned with the relative price of two assets, for example BTC/USD. There is no bitcoin transferred from exchange A to exchange B, simply the trade of USD to BTC on exchange A and BTC to USD on exchange B.
But this post isn't about bitcoin, it's about Ethereum. Ethereum is where all the innovation and most of the financial activity occurs. Arbitrage MEV comes from different onchain decentralized exchanges, slippage, defi liquidations, etc.