The content of rule books, the sanctions available to regulators, and the composition of regulatory bodies are not trivial issues. But the principal reason both press and financial services regulation were lax is that political leaders wanted them to be lax.
In one case this is because they were intimidated by the perceived power of the press; in the other because they held an exaggerated view of the economic importance of the financial services industry and of the abilities of those who led it.
Regulation, guns and broadcasting come to mind. Also the precious movie industry.