IMMORTAN JOE: Do not, my friends, become addicted to water. It will take hold of you, and you will resent its absence.
We're pretty sure you can't become "addicted" to something that is utterly necessary for survival, but we digress. What we see here is a warlord taking total control of an essential natural resource. Immortan Joe controls the water, therefore he controls the people who desperately need that water in order to, you know, not die.
TOAST THE KNOWING: Whatever happens, we're going to the Green Place.
CHEEDO: The stupid Green Place. We don't even know where to find it.
The wives are devastated when Angharad dies, but what's even more devastating is when they find out that the Green Place doesn't even exist anymore. How could it, when the earth has gone so sour?
NUX: There's high ground, just beyond that thing.
CAPABLE: He means the tree.
NUX: Yeah. Tree.
Imagine living in a world that doesn't have any trees. Heck, imagine living in a world that hasn't seen a tree grow in so long that you completely forget what the thing even is.
FURIOSA: I can't wait for them to see it.
THE KEEPER OF THE SEEDS: See? See what?
FURIOSA: Home. The Green Place.
THE VUVALINI: But if you came from the West, you passed it.
THE DAG: The Crows. The creepy place with all the crows.
THE VUVALINI: The soil.
THE KEEPER OF THE SEEDS: We had to get out.
THE VUVALINI: We had no water.
THE KEEPER OF THE SEEDS: The water was filth.
THE VUVALINI: It was poisoned. It was sour.
THE VUVALINI: And then the crows came.
THE VUVALINI: We couldn't grow anything.
Here the Vuvalini dash any hopes the wives and Furiosa had of a nice bucolic existence in the Green Place. It may have taken longer, but the ecological apocalypse (ecopocalypse?) got there eventually. Nothing is safe—especially if it's green.
THE KEEPER OF THE SEEDS: Take a peek.
THE DAG: Seeds.
THE KEEPER OF THE SEEDS: These are from home. Heirlooms. The real thing. I plant one every chance I get.
THE DAG: Where?
THE KEEPER OF THE SEEDS: So far, nothing's took. Earth's too sour.
THE DAG: Ah, so many different kinds.
THE KEEPER OF THE SEEDS: Trees, flowers, fruit. Back then, everyone had their fill. Back then, there was no need to snap anybody.
In this quick exchange with the Dag, the Keeper of the Seeds reminds the audience that the whole reason the world is so violent is that nothing grows in it anymore. If they could make the world green again—which she's trying her darndest to do—there would be no need to "snap" or kill anyone.
FURIOSA: The Citadel.
VUVALINI: What's there to find at the Citadel.
TOAST: And water. There's a ridiculous amount of clear water. And a lot of crops.
THE DAG: It's got everything you need.
It's got everything you need, all right. In fact, it's got everything everyone needs—it just needs people in power who aren't going to horde it all for themselves. People like, say, the Vuvalini and the wives?