system
Given the following post, respond as if you're commenting on Reddit:
human
[DC] ELI5 - If Green Lanterns are set to be 1/sector, how are there so many on Earth?

Hal Jordan took over for Abin Sur when the latter died, becoming the Green Lantern for Sector 2814, and was chosen over Guy Gardner because he was closer.  But then how did Guy end up with a power ring?  And then how about John Stewart, Kyle Rayner, and Simon Baz, for that matter?

Alan Scott, I have a vague understanding that his power ring actually came from a meteor and is only roughly connected to the Guardians and Oa, but what is his role in modern times?  Does he just hang out with Jay Garrick playing Bridge or something?
gpt
Basically:

Hal Jordan took over for Abin Sur. At one point, Hal slipped in the tub, knocking himself out, and there was an emergency that lead to Guy Gardner getting the power ring for a little bit.

Eventually, Gardner got hurt. Bad. This lead to John Stewart becoming Hal's replacement if Hal was ever in trouble. Or, like what eventually happened, Hal quit being a Lantern.

Then the Crisis happened. Guy woke up from his coma and was called to the Guardians to help stabilize things, since John was already busy trying to save the multiverse. During the Crisis, the Anti-Monitor wiped out a full third of the Green Lantern Corps. Afterwards, all three of them were allowed to remain on active duty due to their reduced numbers, and Guy went into training.

More importantly to your question: The Guardians rescinded the 'one per sector' rule because they realized that it caused some of their Lanterns to be babysitters and not actual space cops. During this time, Earth had *seven* Green Lanterns: Ch'p, Kilowog, Hal, John, Katma, Salaak, and Arisia. Guy flickered in and out of the group as he pleased.

More stuff happened, and Coast City was destroyed. Hal went nuts and destroyed the Green Lantern Corps, leading Ganthet to give Kyle Rayner the last, most powerful power ring available. No yellow weakness, no time limit, and (apparently) a larger charge than any of the modern rings.

Fast forward a few years and Hal came back to life, leading to the rebirth of the entire Green Lantern Corps. The Guardians made a new rule: Two Lanterns to every Sector. This meant that Guy and Kyle moved to Oa, while Hal and John got to chill on Earth. Well, eventually some more stuff went down. Hal 'died', so his ring went to Simon Baz. When Hal came back to life, he got his old ring back, but Simon got to keep his Lantern status.

And that's how Earth ended up with five Lanterns again.