The question is what criteria vBulletin uses for ‘active users’ vs. Discourse. They may not be the same.
It would be interesting to see the Discourse statistics after the changeover. How has activity changed according to Discourse over the past year?
I found this post by @engineer_comp_geek from Sep last year, where he shows stats from Alexa:
That doesn’t seem to show much change after we switched to Discourse.