It also has to do with LJ being taken over people who don't understand the users, don't care about the users (beyond a couple of high-value ad-churning ones) an

It also has to do with LJ being taken over people who don't understand the users, don't care about the users (beyond a couple of high-value ad-churning ones) and didn't value the communities existing there while they existed, seeing LJ solely as a traffic monetization platform. So people moved on. And of course the move to Russia - with all content being now rules by Russian law, with its internationally famous regard to human rights and freedom of speech - hasn't helped much for international users either. But I think the main decline started when the platform moved from people for whom it was a beloved child to people to whom it was just a milking cow for producing ad dollars. All we see now is just the final stages of that decline.