The Annunaki didn't come here to mine for gold to replenish their atmosphere
Well, not in the way we think of it.
They wanted gold, sure, because gold is the way to the Philosopher's Stone, the Lapis Philosophorum. But if you think of gold as a shiny metal that can be found in the ground, you're wrong, at least in this reference to it.
HUMANS are gold. Have you ever looked at human blood under a microscope? It's not red, or blue, but a lovely amber-golden color. That should be the first big clue.
There are other species in the universe, but humans were supposed to be the pinnacle of God's work before we fell: we were to be immortal, to be godlike.
The Annunaki, the serpents, were cursed from their inception with mortality and baselessness, ergo they were on a quest to hunt down and take mankind's divinity; our gold, which would enable them to construct the Philosopher's Stone and achieve godhood.
Whether they were successful or not I can't say because not even I know the whole story. However I think the Annunaki interference may've actually caused the fall. Perhaps they were gunning for us even back then.
If they were successful, does that explain why our world has been in such a sorry state throughout human history? Are the ascendent Annunaki actually Ialdabaoth, the corrupt deity the Gnostics warned us about? I believe alien abductions and hybridization programs are still occurring. I truly believe that human genetic material is the key that ties all of these esoteric theories together.
This just came to me in a burst of inspiration so sorry if it came across as a little rambling.