Earlier quoted context omitted.
Can you elaborate on exactly how "big four banks" built a regulatory moat that no one can breach?
The regulatory costs of running a bank are much higher now than before the financial crisis. This means that the chance of an upstart challenging the big players has actually gone down, even though some of the regulation was meant to address concerns of "too big to fail".
https://www.washingtonpost.com/business/economy/10-years-aft...