A few of them change their nic.

A few lurk occasionally.

Some were affable intel gatherers in the doxing days or otherwise secretly haters, and disappeared without ever being discovered.

Some went on to have a family.

Some like to be stars of the hot current controversial topic and lost interest when the media gave up on the great pedo scare.

There is the unfortunate reality of death that comes with passage of time.

Some people get highly butt-hurt by anonymous names that hold opinions different from their own and go on a lifelong one-man boycott to punish this place.

Some people maybe took a risk that didn't work out in their favor.

I am sure plenty forgot their old password and for a long time there has been no admin to assist, or it's infrequent. Like, inexplicably recently 9 new posters got registered. How many other emails go unanswered? I myself don't even know which email addresses are still valid.

Cangee pops in occasionally but has a life now. At least one other on your list left me memo exchanges in the chat a year or two ago, but I don't know if I'd have permission to tell who it was, so I won't. They could have security reasons for disappearing.