I think this is a natural progression. There was an initial period of excitement because atheists could find each other on the Internet. But “atheist” is a not a group, it’s a label for people who don’t accept the religion label - like a social group for people who don’t play golf. There is no common positive trait to link all atheists. When the initial excitement of meeting like minds wears off they move on to some other positive interest, be it social justice or something else.
That said, atheism, new or old, is better off without the anti-social justice-ers, misogynists, anarchists, philatelists, and militant rebels-without-a-clue.