So the TL;DR is a) SOX forced companies to improve internal controls, which we can all agree is a good thing, and b) when things still go wrong, the execs are usually committing other crimes that make it more feasible to prosecute those instead.

Seems to me to me more legal inside baseball than an indication execs are getting away with more fraud than before. Seems prosecutors are just choosing to charge other crimes when they know they have a good case.