Some of the regulars are busy with other commitments (education, jobs, conspiracies, etc.). The substantive contributions to the forum are predominantly writing, which tend to be posted rather slowly. We've never really had a tradition of moderately active discussions on the forums (politics, etc.) or the usual forum chatter (unless you count the now-resurrected Daily Poll). I'm not concerned as long as the world-building community does not collapse entirely.
Also, since the regional government is more or less settled, there isn't much left to do there either (this also happened last time we had a revival, so it's no surprise). Without meaningful controversy, the forum government just has nothing to do except re-elect itself.