This helped nudge my memory. But it's interesting that it did not show up in my family activity feed.
*I* was the cause of the downfall. (Slap to forehead.)
After reading about a policy that did not exist at the time I created profiles for some close (and living) family members, I asked Admin to delete some profiles of living people from whom I did not have explicit permission (my siblings and their spouses; one niece).
This detached me from several branches-- for example, I'd worked my brother-in-law's LEWIN line back MANY generations, AND through my niece, I was connected to the famous Musk family. That profile deletion alone probably caused the massive drop.
So I'll have to figure out how to bring my CC7 back up without involving living people.