I’m not sure that there needs to be a any grand cosmic reason for life to exist. Life could just be an accident of random events in our little corner of the universe.
Natural selection offers an explanation for how life changes across generations in response to challenges in the environment. It does not require a plan, just that the outcome of a chaotic process (reproduction) creates mutations that produce a slight edge, or at least no reduction in reproductive efficiency.
I think the primary defense is the decentralized nature of the application…
Moderators/admins can block and remove content on the instace(s) they control, but this does not impact the content of any other instance.
Effective censorship of the entire ecosystem would require control of many instances and defederation from those that are not deemed appropriate.
There is not really a way for the operator of one instance to control the moderation decisions of the operator(s) of any other instance.