From the bottom graph, it looks like you were getting around 100 requests per second on average, with a peak of around 140, and a total of roughly 12000 requests.
For a static website, that would be child's play even for your humble mini-server, but Mastodon must be doing a lot more work to serve each request than a static web server would.
I've never run Mastodon myself, so it's kind of interesting to see stuff like this.