These are not vague, arbitray statutes. The laws in question are quite old, and include such gems as "federal charges of extortion under the Hobbs Act", "securities fraud and conspiracy to commit same", and "intentional interference in interstate commerce and -- in the cover-up that ensued -- obstruction of justice". These are not non-crime "crimes" that people commit every day by a long shot.
The reason Christie is at risk of going down while the banksters and other big-shots have not in recent years are complicated, but key are the facts that Christie has a lot of enemies, esp. among democrats as he's a nasty shit, that the crimes are easy to understand, and probably the most important one -- a U.S. attorney was assigned to the case. I know it sounds ridiculous, but in the case of the housing bubble and the massive mortgage and securities fraud at the heart of it, the FBI and Justice Department internally redefined the fraud to only exist where a homeowner lied on her loan application. This is what happens when you partner with the Mortgage Bankers Association, as the FBI did, to root out mortgage fraud. It would be funny if it wasn't so damned tragic. There are lots of reasons why the banksters still have gone down and I don't want to oversimplify, but another important reason is that when politicians commit crimes they don't have a corporation to hide behind. But the main reason they've consistently avoided prosecution is Obama. He's a better friend to these fucks than W ever was. Its really that simple. He has protected them at every step of the way, for crimes related to and committed during and after the housing bubble right up to the drug cartel money laundering cases of last year.