So they bought DejaNews and slapped a deliberately bad UI onto it. And as every ISP dropped Usenet, people were told "Go to Google Groups to keep talking."
And because the UX was outright worse than the newsreaders they had been using (no killfiles, no moderation for spam, etc), people left for forums.
Nowadays all you get when you search for Usenet providers are folks dedicated to binaries. Piracy won and smothered out discussion in the process. Even the Usenet sub on Reddit is just discussions that toe the line on Reddit's piracy rules.
The only text-only provider I'm still aware of is Eternal-September. I've heard of SDF offering newsgroups as well but I haven't looked into it.
Its current snake head is the UK's online safety bill.