I have to laugh at the article. The people I knew were not blowing 2600 tones into multi-frequency trunks, they were not even logging into their local TIRKS or SARTS or COSMOS or 5ESS/DMS-100 switch. They had the whole system "owned". The x.25 networks to - Tymnet, Telenet etc. As well as all the key Internet machines and networks. We're going back over 20 years though...Not that I think things are more secure, the opposite actually.
One of the guys I knew later went to work for the tiger team of one of the big four accounting firms. Their success rate? 100%. He complained it was not a real test though, as he could not hack into Verizon or AT&T and get in via those back channels...
As to what happened? Others I know set 1995 as the year it ended, and I agree. Between 1994 and 1996, everyone I know started working at ISPs, security companies, dot coms and so forth. Including myself. Some of the people who hung out on the IRC channels became CEO/CTO/CIO/CSO executives in companies which got millions in VC (back then and recently), or were bought out for millions, or their companies IPO'd. I would say how well some of the people who used to hang out on IRC and go to cons have done, but I don't think people would believe me. I'm not even counting stuff like the founding of Apple, which I think Jobs said would not have happened if him and Woz didn't build blue boxes. The way things really happen are covered up, or not brought up any how. "Every fortune of unknown origin began with a crime" - Balzac