>>107051997On surface level, it's a sugar/salt thing. Aang is sweet and caring and Azula is domineering and controling., they go together like a reese's cup In addition to that they'd be the ultimate power couple; The Avatar and the prodigy princess.
Plus both of them shoulder heavy burdens; Aang with duties to the world as the Avatar, and Azula with the expectations of her nation and her father. There would be a kindred spirit thing between them.