I think the issue is, in order to actually prosecute specific individuals criminally, the government would have had to prove that they indeed intended to launde

I think the issue is, in order to actually prosecute specific individuals criminally, the government would have had to prove that they indeed intended to launder money, as opposed to say make it easier for Mexican factories to pay suppliers in the US. Criminal burden of proof is much higher than the one required for a civil prosecution. The fact that the bank very openly subverted the money laundering controls probably makes it HARDER to prosecute, not easier since they probably also had legal language describing all the legitimate reasons for doing so, etc.