If aether is dense enough it will drown out dynamis. It's why the Ancients weren't directly affected by the Metiea. While their thinner in aether creations were. Dynamis is kind of like air. It's always there but you won't see it unless you inject something into it to make it visible. The reason we weren't being affected by it was due to Zodiark's shielding. Once Zodiark died his shielding faded away and allowing the planet and us to be susceptible to dynamis once more. Well once more for the planet in general.