Matt Levine looked into these competing theories and came up with more evidence for the view that harsh regulators get hired by banks more than lax regulators:
https://www.bloomberg.com/view/articles/2014-06-26/strict-re...
https://www.bloomberg.com/view/articles/2014-06-26/strict-re...
Business is a parimutuel system: something that harms your company can actually be beneficial if it utterly demolishes your competitors. Many regulations are of this form. They are expensive and difficult to comply with for big companies, but they are impossible to comply with for small companies, and thus keep competing startups out of the market entirely.
Usually, people make the opposite argurment. That laws won't be harsh enough. And the evidence proved that wrong.