There were over 8 million Google+ Communities formed. Roughly 10,000 of those had > 10k members, based on my own analysis of a data extract of these:

<https://social.antefriguserat.de/index.php/Migrating_Google%...>

The absolute obliteration of online groups was inexcusable, most especially as there were not provisions made for exporting or supporting contact, and in fact active obstruction of attempts to the same.