The US wants Venezuela's oil fields to be privatized and the Maduro government has nationalized the oil fields to prevent them from being owned by US/mult-national corporations for profit.

As with any government that nationalizes their resources, the US will totally obliterate their country for the offense of daring to protect their interests against USA's interests. See Libya and Iran as but two examples.

Also note that, as has been publicly state, the CIA is doing a lot of the work here and has been "authorized" to operate in Venezuela. The CIA was created by the Dulles Brothers specifically to protect the interests of US businesses around the world.