Iran is a major oil producer and know precisely where to damage oil facilities.
It has successfully attacked Saudi Arabia from Yemen with drones and cruise missiles in combination (drones to take out air defences.)
It has unsuccessfully tried to attack Israel with drones, but Israeli air defences are far superior to the aged US Patriot system used by the Saudis.
Saudi is (for better or worse) a major US ally and there is no way Israel or the US would attack it and endanger the world economy on which they both rely. The last thing Trump needs is a big oil price spike running into an election year. That is why Iran was willing to try such a daring and dramatic attack.

The precision of the attack proves that Iran knows what it is doing when it comes to drone warfare and oil facilities, at least against a weaker opponent, like Saudi.
It justifies the many Israeli strikes on Iranian drone facilities in Syria and Iraq. If not for these strikes many Israeli critical facilities would have been hit by Iranian drones.

Check out my related post on the topic. https://steempeak.com/saudi/@apshamilton/putin-offers-to-sell-s400-to-saudi-but-actually-only-israeli-air-defenses-are-proven-against-drones-v1qukuyo