Above all, Schneiderman is looking for a big, public case to build his credentials - that’s how AG’s in NY did it - Spitzer, Cuomo, etc...
Of course, a nice big shake-down “settlement” from the targets is another goal, which will be used to fund plenty of campaigns and foot-soldiers for future elections for Schneiderman
The guy is corrupt as can be.
Oil companies have lots of good lawyers. It is not the job of Congress to run interference for them.