Those are kind of the opposite of each other.
Fascism is the control of corporations and other business entities by the government (but not government ownership).
Oligarchy is the control of the government by wealthy individuals (who do not hold government positions).
The Pope is Argentine. The ruling Peronist party in Argentina is Fascist, and has been Fascist, since Hitler was in power in Germany. I guess the Pope is just true to his "roots".
And the circle behind that government is what you call "oligarchs". Whether the circle forms the government, or the circle is formed by the government, it winds up being the same.
Chavez, the communist, built a fascist government. The people at the top who held him in power (whose companies were protected) would be the oligarchs. They might not be the same people as the previous pre-Chavez oligarchy, but they are oligarchs just the same.
We tend to think things like fascists, communists, oligarchs, as being distinct and exclusive when in fact they travel together.