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human
[DBZ] When Goku and Vegeta removed MajinBuu from Super Buu why did he revert to Kid Buu and not Evil Buu?

From what I remember Kid Buu became Majin Buu after absorbing Grand Supreme Kai. But that had occurred so long ago the process was irreversible. So when Majin Buu got rid of his evil energy he formed Evil Buu and not Kid Buu. And to form Super Buu; Evil Buu absorbed Majin Buu. So I mean logically when they removed Majin Buu from Super Buu he should have gone back to Evil Buu rather than Kid Buu.
gpt
Evil Buu was comprised of a portion of the original's power without the grand supreme Kai's influence. He was Buu but not enough Buu to form Kid Buu. When Goku and King Vegeta removed Fat Buu, evil Buu had a higher concentration of the original's power and became Kid Buu. 

This raises an interesting side question, How much more powerful was the original Buu than Kid Buu? Considering that Fat Buu still had some of his power during the final battle: