but in the end you are not punishing the bank, it merely is an entity with no physical means of being punished. To punish it you need to throw their boards into jail.

Fines are paid by share holders if any, hence is the bank punished? Not unless depositors leave in droves. You cannot fine a bank for its holdings as those are the funds and properties of other people, the bank is merely managing money for others.

if you attempt to dissolve a bank, who takes over the loans, how do you get the depositor funds back. You cannot confiscate them in the names of the state, the distress to the economy would be drastic.

In the end its back to the people running the show, put them in jail, or force them out, or fine them, or all of the above. However like politicians there are so many levels here than they are nearly immune to their actions

TL;DR

Monetary fines are irrelevant, punishing the people who run it is the only means to correct future behavior