I don't think that anyone knows for sure what happened to ASSTR, but but I saw a post earlier today that offered a plausible explanation for its' disappearance.
It was probably a combination of several factors: financial, legal, and personal, with the legal factors potentially being foremost.
Many of you may be aware of the McCoy and MrDouble (Thomas Arthur) cases. Frank McCoy was both an author and editor, whose materials were featured on ASSTR. Like virtually all the materials on ASSTR, they were text-only.
Frank McCoy was charged by a Georgia grand jury in 2008, of violating 18 USC 1462, by transmitting a link to where obscene materials may be found. He had a bench trial in January 2010, and a guilty verdict was handed down in 2013.
McCoy was sentenced to a little over 2 years in jail. He appealed both his sentence and conviction. The judgment of the court of appeal came down in June 2015, after McCoy was released, and the court unanimously upheld both the guilty verdict and sentence. In November 2015, McCoy was arrested again, put on trial in December, and convicted as a repeat offender. The judge sentenced him to 10 years in jail. McCoy died in April 2020 of Covid19, still a prisoner.
In 2021, the case of Thomas Alan Arthur, a.k.a. MrDouble was prosecuted. The DOJ news release read in part as follows:
Texas Man Sentenced to 40 Years For Running Website of Stories About Raping, Murdering Children
Thomas Alan Arthur, a 64-year-old Texas man who was convicted by a federal jury for nine counts of obscenity crimes involving children was sentenced, Tuesday, to 40 years in prison.
Arthur was convicted in January 2021 for trafficking textual stories and drawings of child and infant sexual abuse and murder on a website he had run since 1996. Arthur personally reviewed and approved all submissions before publication.
Arthur's case was the second major text-related obscenity conviction in a little over a decade. I think that the ASSTR admin could be forgiven if he decided that continuing to run the site put him in danger of significant legal jeopardy.
The ASSTR.org domain was registered in December, 1998 -- it expires in December, 2022 -- it has been going for 24 years now, and perhaps the operator has just become tired of running the site, and paying for the costs of it. We also don't know who old they are, nor what their health status is.
I suspect the reason to let it go is a confluence of all the above factors.