Makuta made the MoUP because he was jealous of the attention Ekimu's masks got. So why didn't he try to sell the MoUP, or give it to some okotian villager? Why did he try it himself?
Are Makuta's plans ever coherent and well thought out?
Maybe he wanted the ultimate power of mask making? Or maybe it was just he was putting it on as a sign of victory that he had made the island's most powerful mask that his brother didn't, or maybe the mask's influence?
Why sell it? You've just made a Mask of Ultimate Power! Why on Okoto would you wanna give that up? And in that vein, who could you trust with that kinda power besides yourself?
As for why he put it on...well, Ultimate Power is a tantalizing opportunity.
You have a mask that is literally called the mask of ultimate power
Does it really need any more explanation?
The Mask of Ultimate Power presumably gives you control of nature itself; wearing it effectively makes you into a god.
There's no better way to get attention than to control literally everything.
He was fueled with jealousy. Sometimes when you are jealous, you don't think straight.
I personally believe that Makuta put MoUP on simply just to prove to Ekimu that it's legit MoUP.
Makuta was jealous of villagers' love for Ekimu's masks. So it wouldn't be surprising for him, in order to prove himself worthy, to create the forbidden "ultimate" mask. And after he created it, he need to put it on to show that it does indeed possess the "ultimate power". How else would they knew that it's not just some defective attempt to make the "real" MoUP?
I think he knew that this could go horribly wrong, so he managed to convince Ekimu to travel from the City of the Mask Makers to opposite side of the island before he tried it on.
Anyway, that's just my take on it.
Well, presumably Ekimu's MoC is what helps him make such amazing masks, it could be Makuta put on the MoUP to try and help him make better masks...
but then again he made the MoUP...
...Maybe he wanted to make a Mask of EVEN MORE ULTIMATE POWER!
Edited title -- 21sselliW
The real question is "how could he possibly justify losing to anyone once he had it "
Because he knows what's best in life.
well, let's think about it
he was super jealous of his brother because he was working hard on other masks while he was getting little to no praise for his, he felt unappreciated. So he wanted to prove he could be as good as Ekimu and break the law they made in order to do so. He thought that he would test it out and prove how much more powerful it was just so he could be appreciated more.
ended up overpowering him and making him nuts
Because Bionicle G2 needed a villain.
because he just wanted to be more powerful than ekimu