Hang on, what happened to their blog???
I didn't check on this blog for a while, so I'm sorry for the late reply!
As for the question, I'm not really sure either. Since their profile picture turned blank and we can't visit their blog anymore, I assume that they deleted their blog and presences (or at least all that we know of) on tumblr.
This is just me speculating, but I think this might had to do with those horrible people on 4chan who kept harrasing them and sending them dead threats on their inbox. I remember seeing them addressing this issue on january (they turned off the reblog feature so there's no trace of it) and they made the decision to stop posting any new utdr posts and just reblogging/adding things to other people's posts.
That went pretty well for a while, so I assumed that things were going a little better for them, but I guess that wasn't the case. One day I just realized that they disappeared, no notice or anything. Tried to search up and visit their blogs, nothing. Tried to search for anyone who notice the same thing, nothing. It felt like they silently disappeared one day without anyone realizing.
With that being said, I respect their decision and hope that they live their best life without all the drama and harassment. It's just such a shame that we lost a lot of their utdr analysis and friendship propagandas over the years. Most of their long posts with the 'read more' feature can't be fully seen anymore, but at least there are shorter ones that survived due to people reblogging them. I'm trying my best to archive all of the remains here, so people can find them easily in one place.
Also, those 4chan people can go fuck off. Congrats, you just ruined something that's supposed to bring fun and enjoyment to a lot of people. If that's your idea of what happiness is, go get some help.