Regular social networks run on data centres with just as much redundancy and decentralisation from the technical perspective. If anything, in the Fediverse only content that people actively seek gets duplicated to other instances, so the overall energy requirement is smaller.
On the other hand, I can’t compare the effectiveness of small Pi computers people running at home for their instances, and huge server farms. I guess it’s comparable to some degree, as most likely both use some shared resources and are also used for other things.