They have has as much of a seat as warrants their size and economic power, perhaps even more because of their location as a buffer against China. Most EU countries have pull only because they are part of the EU. Compare Spain and Japan on the world stage, for example.
They control moderation, as they also do on Reddit. I don’t know about Lemmy but I have personally been shadowbanned on their Reddit sub. They can’t do that on Mastodon.