The DEA and every other agency in the drug war has a persistant problem with agents turning to dealing drugs. They know how much money is involved, have access to difficult to trace drugs and know how to avoid the police.
As for spying on the government, for all we know they may have been looking for people dealing drugs on their side, nor do we have any proof that it really happened.
The whole thing strikes me as a few agents dealing drugs on their own, and the Venezuelan government taking for action of the US government.
Jay