So I was just wondering...How did Maleficent become the ruler of the heartless? Was she just the first person to discover them and harness their power to control them? And why didn't any of the other villains try to overthrow her?
We really don't know all the details, but the heartless tend to join whose ever side is strongest as Saix said in KH1. No, Xehanhort would be credited with that one. I bet they would have, but Sora beat most of them before they got the chance. Plus they wanted the to open the power of the DTD and none of them lived or weren't around to be there and stab the old hag in the back.
Yes then, If we go by Disney Villians yes she would. The heartless were created in Hollow Bastion, she found the castle empty except for the heartless and basically took over.
The heartless followed every disney villian, but since Maleficent was the darkest out of them all, most followed her.
While we're on the topic of heartless control, we have a plot hole. Sora was easily strong enough to control the heartless (he got how many nobodies?!) but he couldn't because they feared the keyblade and as such, attacked him. Now why couldn't he control them when he was without it for some time after Riku took it?
Because if he did, he would let himself be a part of the darkness, and I don't think he would do that; sacrifice his light for dark.
She didn't destroy the world just the city and cleared out the place by using the heartless. After Xehanhort cast himself into darkness hollow bastion found it's self with out a leader. The old hag sat down and took over. Using the heartless she stole the hearts of many of the people of hollow bastion. Most of the people either had their hearts taken or escaped to other worlds like Loen and the gang. This was 9 years before KH1. Since then the city was abandoned, Maleficent used it as her headquarters as A) she and her evil buddies could work in peace and B) she could bring the Princess of Hearts here to open the DTD.
What William said. The Heartless followed Maleficent because of her power. I guess you can say she had a strong heart, but she was able to use the Darkness efficiently. BUT if she showed one moment of weakness, the Heartless would've taken her heart. The Heartless side with who's strongest, but they think with instinct. So if they have a chance to take that heart, they would've. Sora wouldn't have been able to control the Heartless because he never used the Darkness in his heart. Otherwise, he probably wouldn't have been the Keybearer of Light.
Sora's power is linked to his heart's strength. The reason Riku could take the Keyblade from Sora in the first place was because he had given Sora doubt about whether or not he was really the Keyblade Master, so his heart was weaker for a short time. This weakness would be why he would not be able to control Heartless. And even if he could, he wouldn't because he is far too lightsided to utilise his darkness.