I did some digging.
Apparently it was
Zordon who trapped Rita. Zordon and Rita, who are both basically Sorcerers of some kind, were in a war against one another for about 2k years on Earth. Rita started to lose the battle and decided to fake a truce, meet with Zordon to discuss peace terms, and then fuck him over.
Zordon didn't trust her, and what ended up happening was that Rita trapped Zordon "outside of regular space and time" in that tube, while Zordon trapped Rita in that space dumpster "for eternity". Eventually Rita was released by silly human astronauts and Zordon existed in the "tube" until another Power Rangers series saw the Red Ranger smash it open, which spread Zordon's good energy across the universe, TURNING BOTH RITA AND LORD ZED INTO GOOD GUY HUMAN BEINGS??!?
Except you know, it just ejected their evil energy which wandered around until finding new hosts.
... O_O
Lindsay - Jan 13, 1990 - July 17, 2023
Thank you for fighting the fight for so long for me.