Many people left because the forum is overrun by spammers.
Not quite true.
This is the obvious answer. It's hard to get a decent discussion going here. Either it gets overrun with spammers, or those desperate to gain rank with negligible value posting, or it gets moved to off topic by a mod, and then it falls off the first index page before your mouse can get its clicker out.
Well, you can always start a self moderated thread and if the thread in it's appropriate board, it never gets moved by the mods.(I have never experienced at least).The thread falling off the first index is very true and you can't help it.