I think the centralization on mastodon.social is a bit over estimated. According to fedidb.com there are over 1.1M active users in the fediverse. Of these mastodon.social has about 273k. That means mastodon.social has about 1/4 of the active users. The rest are scattered over nearly 43k servers. So I'd say the fediverse is pretty decentralized. That would make it pretty resilient.