Similar to Mastodon's spikes last year, it seems. Anyways, there is data to think about. Source
You are only shown what your server has stored. Your server only stores what people of your instance have subscribed to. If you visit bogger instances, they all have different Hot feeds, because each server pulls different content. There is no one way to see what is going on in all of the fediverse. You are only ever shown a part.