If we take the example of the UK, all of the bank failures were because of non investment banking activities. RBS failed because of its excess of leverage as a result of its disastrous acquisition of ABN AMRO and because of its loan book, HBOS because of its loan book (essentially commercial real estate exposures), and Northern Rock because of their over-reliance on wholesale funding.
There are examples of banks failing or making large losses because of the investment banking activities (Lehman, Merrill, Bear Stearn, UBS) but my point is rather that the principle "Retail banking = safe, Investment banking = risky" is simply not true.
In a way, universal banks tend to be more robust than a specialized bank, as it benefits from funding and revenues diversification (and cheer size to absorb losses).
> we didn't pursue many personal penalties nor criminal cases
I am not saying that there hasn't been any fraud in the financial crisis but I am of the opinion that it is not fraud that caused this crisis. It is the over-reliance on leverage, short term funding, and a belief that the US real estate market would never go down (belief that many people have today in the UK).
You can't send people to jail for making bad business decisions. Some banks were run in a moronic way, but being incompetent or missing a fundamental economic driver is not a crime.