Why Earth?

[Super Cena]

Why does Earth get attacked so much?

[MattEmily]

MMPR = Rita had attacked it since it was the closest to the Moon. Lord Zedd had just continued it since it kept on getting in their way and Master Vile followed suit but really all Master Vile wanted was the Zeo Crystal.

Zeo = the Earth was chosen as the Machine Empire's target mainly because of Rita and Zedd's interest in it.

Turbo = Divatox had no interest in attacking the planet until the Rangers had ruined her wedding.

Space = There was no reason other than 4 of the Rangers were from Earth so Astronema just wound up using it to her advantage when she needed one.

Lightspeed = Mariner Bay was built on top of the demons' Palace which is why that was their target.

Time Force and Wild Force = we really didn't have a reason for this. My best guess for Wild Force is because Turtle Cove Lake is presumably where the Animarium came from.

Ninja Storm = Blue Bay Harbor was the target because that was where the Abyss of Evil was at.

Dino Thunder = presumably only because Tommy was there.
SPD = only because of Cruger.
Mystic Force = I don't believe there was a true reason other than they wanted the Light.
Overdrive = There was no reason other than they wanted the jewels and the crown the crowd was originally in Andrew's possession.
Jungle Fury = it was the planet that Dai Shi was trapped in a box on.
RPM = it was likely the last planet that had any defenses for the Venjix Virus.
Samurai = likely because the Nighlok was aware of a new group of Samurai Rangers being put in place.
Megaforce = there was no reason.
Dino Charge = it was when Sledge had lost his asteroids due to Keeper's bomb as a result of Sledge wanting the Energems. He likely figured the gems and Keeper would still be on Earth which is why that was his target.

[Captain Codfish]

For some of those later seasons, the threats originated on Earth. So its more the early years that are the question. Rita wanted Earth because thats where she left off. Zordon being there was probably part of it too. Zedd wanted to conquer Earth due to Rita embarrashing him by failing to defeat at the Rangers. Thr Machine Empire saw it as part of the last galaxy they wanted to conquer. Divatox followed Lerigot and wound up coming back for revenge. Astronema was just following the Rangers. During C2D the whole galaxy was under attack so it wasn't just Earth.

[Zordon's Legacy Exposed]

Zedd lost his Dark Galaxy to Vile. He saw conquering the Earth as a way to save face and start to rebuild his empire. If he was able to destory Zordon and his Rangers he would earn much respect from his peers and gain a lot of his standing back in the UAE. He just punished Rita to use her as a scapegoat and to take his anger out on her. He felt he didn't need her anyway.

[Ranger Master]

I don't think Zedd even cared about Earth until he lost the Dark Galaxy. He had 10,000 years to conquer it. Why didn't he take over for Rita then?. He even let her be for a year.

[Doomsday]

Word of Zordon being alive and active on Earth took a year to get out. Once Zedd heard about this he had to take an interest on Earth. Since taking out Zordon would have been an amazing feat. And they were old rivals. The Dark Galaxy was actually conquered while Zedd was trying to conquer Earth. His obssession with Earth ruined his standing in the UAE. Thats why Zedd and Rita leave. To re-conquer most of his old territory. Of course this ends up putting Vile and Rita against each other. Just after Vile just bailed them out of the Machine mess. But the UAE were a bunch of backstabers anyway.

[Captain Mutiny]

There were so many ancient artificats and trapped Villains, Earth was the perfect place to want to conquer. You could have much power and recruit a whole army of trapped villans. This woukd have given the early villains the chance to take control of the whole UAE. And thats not even considering the fact taking out Zordon would have been a great strategic advantage to the UAE.

[Diabolico Rising]

Earth waa just home to a lot of villains like the Lightspeed Villains.

[Super Zeo Ranger]

I think the bad guys just want it. Its a planet with lot of resources and powerful artifacts.

[VR Master]

I think it has a lot to do with the Morphing Masters being based there in ancient times.

[Quasar Saber]

The question really should be why not Earth?

[Zordon's Legacy Exposed]

Earth was definitely important to all factions. There was a good reason for Zordon to be there. Of course it was also to engineer the human race to become soldiers in his war. Which makes Earth even more attractive to the UAE.