Ending, plot discussion. Warning: Spoilers

[kimoi]

Maybe the seal didn't work because the world's aether was drained by the avatars and the avatars were drained by dalamud?

Thus making the 12 weaker and Bahamut stronger?

I tend to agree with this. There seems to be a lot of curiosity of why the Twelve couldn't stop Bahamut. But perhaps this isn't the case. The Twelve were stronger than him in the past and are usually stronger, but with all the aether problems recently their power has waned and Dalamud and its inhabitant has grown.