system
Given the following post, respond as if you're commenting on Reddit:
human
[Avatar] Is there a reason the avatars follow a cycle?

Why does the avatar cycle follow the order of the season fire, air, water and earth? Does it matter? Theoretically couldn’t Raava just choose whoever she wants to be the next avatar and it would essentially make no difference? What gave her the idea to go in this order in the first place? In ATLA it works out because Aang is the last airbender but imagine the next avatar is an earth bender but there are only 1 waterbender left wouldn’t it make more sense to simply skip earth and go to water and thus preserve the knowledge?
gpt
Fire, Air, Water, Earth. 

The order Avatar Wan was granted the elements by the Lion Turtles. 

Coincidence? Maybe. 

But Raava is the spiritual personification of Order. It's possible bonding with her forces Wan's natural reincarnation into a more orderly pattern, each nation in turn.