Lots of users were just awarded the Generalist badge 30 minutes ago.
What changed?
It's likely that one or more tags were moved into the top 40 tags recently. This could either be a result of more growth in those tags, or the removal/deprecation of tags previously in the top 40.
With one or more new tags entering the top 40, people who previously only had 18 or 19 tags with good answers who are active in one or more of these tags, would be getting enough good answers in the top 40 tags to get Generalist.
Another possible cause of this occurring, especially if no one has earned the Generalist badge in the past, is that the badge is only awarded to anyone once each of the top 40 tags are being used on at least 200 questions.
Once someone posts a new question that brings the top 40 tags to 200 uses each, or retags a question to make that so, the badge will be awarded to everyone who qualifies for it.