I don't think it was because she was always crazy, or that she couldn't handle managing the fire nation alone, I think it's a number of things like, she had deep mental instabilities, believing her mother favored Zuko over her. And that her father raised her in an environment with no mother-figure, Azula had to be nothing less than perfect. When her friends betrayed her, these instabilities were made clear. And when Sozin's Comet came, Azula was to be crowned Fire Lord but Zuko and Katara defeated her causing her to suffer a total mental collapse. When all these add up I guess that's what happens to you lol.
Sorry, I didn't know which one to pick. :)

Well also because she was obsessed with power...and she got too much power and took it out of everyone and just went insane...

xD

I felt terrible for her all her life she worked hard evryday and night for one goal so she could be fire lord and after all her patiance, training, and hardwork she finally acheived that goal. then as she was being crowned her brother who had betrayed the nation, swooped in and stoll her life from her, she went from being crowned fire lord to prisioner and there was nothing she could do about it.

thad make any one go insane, its so unfair even if she is eveil no one deserves that.

She was always crazy would have been my second choice.XD

someone just needs some help here.

There was too much pressure on her

She wouldn't be in a mental hospital if someone just would of spent some quality time with her.

I think it was because her mother never cared, then it started to get worse when Ty Lee and Mai betrayed her. Then after that her father telling her she wasn't going. Then she finally went insane when she saw her mother in the mirror.

If I made this poll now I probably would have added 'because she wasn't raised right.'

I think it's a combo of all of the above; firstly she thought her mother didn't love her so she was doing all she could to keep her dad's love. Then she loses her two best friends. And then her dad runs off and tells her that he won't be needing her so she felt like she couldn't even keep his love. And to top it off there's a lot of pressure dealing with managing a nation and I don't think Azula was ready for it just then. As TheMyths said, she just needed someone to show her some affection and spend some time with her. She was under so much stress. And she lost everything she worked for.

^ Exactly. Her mind broke down, basically, because her life was too hard for her.

I think she could have handled the nation at another point, but not right then.

@ThisOne Completely agree.