Rita created the green ranger coin with her power. She is a sorceress that practices evil and dabbled into the art of dark magic.

_When he was captured by Rita, the material that had encased Tommy was actually some magic wax, which was linked to his Morphing powers. By turning the wax into a Green Candle, Rita was able to ensure that as the candle burned, his powers would slowly fade away, and when the candle burnt out, she would reclaim his powers for good. _

The Sword of Darkness was why he was under her spell. Once Jason destroyed it, the evil spell was broken. It also enhanced his powers, hence why he almost won.

That explains it. I was wondering how that was played out with the sword.