Here's why:
* Reconciliation and Forgiveness: Zuko finally accepts his father's love, and Iroh accepts Zuko's past choices. This emotional resolution allows them to rebuild their relationship on a foundation of forgiveness and understanding.
* Shared Experiences: They've fought alongside each other, faced challenges together, and supported each other during tough times. These shared experiences create a strong bond between them.
* Mutual Respect: Zuko recognizes Iroh's wisdom and guidance, and Iroh deeply cares for Zuko's well-being. They respect each other's opinions and choices.
While they may not be "best friends" in the traditional sense, their relationship is definitely one of deep love, respect, and understanding.