It never ceased to exist.
A nation CTEs for inactivity after 28 days (or 60 if in vacation mode). 7 days into inactivity its influence also stops growing (whereas normally it grows at ~2 per day), so there should be a three-week flat line in the
influence score graph, followed by the
residency score being reset to zero. This isn't the case.
The only residency reset is due to you moving from "sus is very sus my guy" to "sus is mildly sus my guy" around December 3. You weren't inactive at the time. It looks like your longest stretch inactivity was around 21-22 days (a flat line of 14-15 days in influence).