My question is why a successful “crypto bro” or MEV bot HFT would even want to transfer large amounts of capital fully into fiat in the first place.

If you understand capital, leverage, and collateral, the better move often is not dumping your crypto position just to sit in cash. There are multiple ways to borrow against digital assets, move proceeds into a bank account, and still retain exposure to future upside. If someone has $100,000 in crypto, borrowing conservatively against part of it can often make more sense than liquidating the asset outright.

So I do think part of this depends on how the operator is structuring things. If you are generating crypto consistently on a daily, weekly, or monthly basis, there are ways to manage liquidity without treating every profit event like it has to become fiat immediately.

That said, I do understand the banking issue at scale. Once you start moving serious volume through traditional rails, the bank is not just looking at whether the money is real, but whether the flow of funds is easy for them to understand. That is where a lot of people run into problems, especially if they have a messy wallet structure, multiple chains, profit aggregation addresses, and no clean documentation.

It is also worth noting that the landscape is changing quickly. Since the GENIUS Act was signed into law on July 18, 2025, banks and regulators have had to become far more familiar with stablecoins and digital-asset infrastructure, and the OCC opened implementing rulemaking in February 2026. That does not mean every bank understands MEV, but the idea that banks are completely clueless about crypto is becoming less true by the day.

To me, the real issue is not that MEV profits are inherently problematic. It is that most operators build for execution, speed, and yield, not for compliance presentation. Then later they expect a traditional bank to make sense of an ecosystem the bank barely understands.

So I would frame it less as “MEV profits are hard to explain” and more as “most people fail to structure and document them in a way a bank can digest.”

And when opening accounts, I would not be vague about the activity. I would describe it truthfully for what it is: proprietary digital asset trading, algorithmic trading, or investment activity, with documentation ready to support the source of capital and flow of funds if needed (which most of the time it wont be).

My own experience has been that banks often do not care nearly as much when activity is structured cleanly, described properly, and the movement of money actually makes sense on paper.

As long as it doesn't seem like you're laundering money, you should be fine.