Hi,
Why did the maori migrate to new zealand?

Nothing I've read can explain why. Nor can anyone explain exactly when.

One popular theory was they moved simply due to curiosity, the urge to roam. Many think this migration started as far away as China and took thousands of years. Other mention overcrowding of villages, but I doubt that. Unless you mean too many "Chief's" is overcrowding. And then there's the theory (mostly mine) were the Maori were generally a peace-loving people and didn't like to be oppressed by current conditions, conditions we can now only speculate...