The conclusion to Aang vs. Ozai was foreshadowed just the right amount.1) Third eye (which is what Aang uses to connect with Ozai's energy): Roku’s dragon communicates with Aang by touching his third eye, Aang pacifies Hei Bai through the third eye, Zuko as the Blue Spirit is hit by an arrow in his third eye, Combustion Man bends from a tattoo of a third eye, Aang’s most identifiable feature is a blue arrow that points to his third eye2) "Energy" as a technique/power present everywhere: Guru Pathik says he found Aang in Ba Sing Se through his energy connection with Appa, Aang says he found Appa and Momo in the swamp by using the swamp's energy to track theirs, the arrow tattoos not only point to the third eye but also overall follow the chi paths so they light up alongside the eyes when the Avatar state's energy is awakened3) Blocking chi/energy: Water tribe healers practice on a chi path mannequin, Ty Lee is a combatant specializing in acupressure who can temporarily block bending, Iroh saying the energy is around them and passes through human body in Bitter Work so it's necessary for bending, Aang can’t use his Avatar State because Azula wounded his pathway4) The point is that it's divine intervention as a reward for Aang's spirituality/sticking to his air nomad beliefs. He was literally praying that night (that's why he had a little tray full of candles and fruit offerings) as he was taught to do by the monks and his belief is recognized by a divine entity. It's like Zuko losing his ability to bend but miraculously finding the sun benders and the ancient dragon masters, and Toph miraculously finding the badger moles right when she needed them most as she ran away.
