Yeah, a couple days of temporary spike does not a wave make.
Mastodon (and the Fediverse) tends to see “scalloped” growth: big increases, followed by gradual declines. Every time Musk does something dumb, you see days or weeks of increased signups. Then the new users fall off, and they become inactive. Usually, it stabilizes a little higher than the last wave.
The waves come in, and the tide rises. The weather passes over, but the climate stays stable (or increases).
If Twitter collapses, then the tsunami arrives. :P