Quote Originally Posted by KiritoKhun View Post
do we know why primals started flying out of him
We know that Ceruleum is concentrated and refined Aether, and Aether is released when any living thing dies. We also know that during the many assaults by the Imperial Legion the beast tribes are fervently praying to their gods for deliverance.

It seems reasonable that the release of a huge amount of Aether, through the destruction of the Agrius and the death of Midgardsormr, is enough for the primals to take physical form and answer their followers prayers.

I don't think that's actually supported in any official lore, but it seems to follow what we know of the world and it's primals.