How was the creater of Avatar: The Last Airbender, able to make it almost just like an anime, and how did he know to make wrighting in japanese, did the creater know a lot about japanese culture?

This should go on the Question/Answer thread, it's pinned.

But to answer your question, the creators had seen many japanese films, and anime films (likely series too, the only series they've mentioned seeing is Cowboy Bebop though) and they based on anime artwork for the animation, they also based on many asian cultures for the show, some they knew of, others they researched for.
Lastly, the japanese/chinese symbols are rather easy to find, so i suppose they just checked wikipedia to find them