Well, Zant is honestly one of my favorite characters in the Zelda franchise. I don't know why, but turning from a calm, collected, rather menacing villain into a psychotic and over-dramatic mental case was just one of those "that... was... AWESOME" moments. It was unexpected and, although I felt a smidgen of disappointment, I still liked him. I feel Nintendo didn't do him justice enough by simply showing him as a basket-case and not saying why. I think that's one of their biggest faults, in my opinion. In truth, I think he was driven to his current state by pressure--the Twili seem to be an advanced race focused around stern rules and politics, and politics drive people to do some stupid and crazy things.
I guess I feel he was 'misjudged', as cliché as it sounds. I really do. But simply because of the lack of information and depth. I just highly doubt he was ALWAYS like that. There had to be some reasoning for it, other than wanting power (even though that also drives people to the brink). He and Midna's interaction always hinted for me that there was something between them, and not just the 'crown', so to speak. Whether or not it was what "certain fans" think, I have no idea. But I know something was there. Heck, with her attitude at the beginning, I wouldn't be surprised if she was also one of the causes. But again, we don't know the entire story and it's really a shame. Although, I do think that Ganondorf's influence also helped to drive Zant's mental state into a downwards spiral--more so than it already was. Power like that doesn't just come without consequences.
But, uhm... this is all just my opinion...