Would it be fair during that time if I asked you to hold your PRs, bug tickets and work in general because we're on paid leave?
On-call rotation exists for those reasons. Otherwise, all countries would need to respect all other countries holidays.
In fact, we're not even aware of most US holidays. It is likely to be a coincidence.
What I’m attempting to refer to, is that _if_ this was done with malicious intent, then maybe the hope was that doing it during a holiday would reduce response time or allow it to fly under the radar. Of course, as you say, just because it was a holiday does not inherently mean it’s malicious, it has plausible deniability.
I don't know if there's a rotation or another system. I think there are probably multiple across different parties responsible for maintaining CA trust.