I'm guessing it had to do with how NLC is a textbook troll, pretty much solely posting to get a rise out of people. I guess by the time he moved on to calling people pedophiles etc. even the moderators' patience wore too thin. I'm not sure he was actually banned before the spam epidemic started, it was my impression he caught on to being ignored by so many people and started farming alts. Maybe someone who kept better track of things can comment on that.
Despite my interest in economics, I tend to avoid the economics (and speculation) sub because it is my understanding that they have a lot of trolls and spammy shit posts (maybe this is actually NLC - ironically).