Reddit answers to shareholders and a board of directors. Each fediverse instance is run by its owner and negotiates with other instances to federate.
If some bigshot wants to own reddit or rule it like a totalitarian asshole, he can buy it and vandalize it if he wants to. If some bigshot wants to own the fediverse, good luck buying the thousands of instances that exist and they still wouldn't get us, because we'd move to or create new instances.