Why will managing Venezuela for the U.S. be as difficult or even more difficult than managing the Iraq War?

First of all you have Maduro's supporters. Then you have drug Lords unhappy with Trump being there. Then you will have South Americans who hate America anyway. Then you have rabble Rousers like Putin and Xi who have interests there too. Then you have terrorist groups who finance themselves off of Narco Terrorism, then you have female sexual Slave runners of al sorts too. 

So, you have millions and millions of dollars in various illicit things that are going to cause these multi-million dollar illegal operations to hire Mercenaries to kill American Troops stationed there.

Who actually benefits from all of this?

American Oil Companies allowed to go back and make Billions and Billions of dollars on the most potential oil reserves on earth!