The wrestling world was forever changed when Hulk Hogan formed the villainous New World Order faction with Kevin Nash and Scott Hall in 1996. Before they knew it, WCW was on top of the wrestling world - surpassing the WWF in the Monday Night War ratings.
The nWo became a massive success for WCW, namely because of Hogan's shocking heel turn after being the face of professional wrestling for over a decade. With merchandise sales going through the roof, the nWo is widely recognized as one of the greatest factions in history.
But a major knock against the faction was the fact that Eric Bischoff and the creative team were too devoted to the nWo. Just when the faction appeared to break up, they'd always find a new way to reunite. As the group began to lose its steam, the nWo broke up into two factions: nWo Hollywood (led by Hulk Hogan), and nWo Wolfpac (Kevin Nash, Sting, Scott Hall and others).
Eric Bischoff recently appeared on Chris Featherstone's Pancakes and Powerslams podcast, and explained why the nWo faction was formed:
“The reason why we expanded the nWo, quite frankly, including the reason why we brought in Bret Hart although he had nothing originally to do with the nWo, was because we knew we had launched a second primetime series on the TBS network based on the strength of Nitro on TNT,”
It was a mandate directly from Ted Turner himself, and based on the success we had with Nitro on TNT, Ted was determined, much to my chagrin, and the chagrin of others at the executive level, but Ted was determined to launch this second two-hour show on TBS, and that required two things.”
Bischoff then explained that he pushed towards not having a second television show for WCW, but lost the battle. Once Thunder launched, Bischoff tried to create a similar rivalry to the SmackDown vs. Raw. He worked to have a Nitro vs. Thunder rivalry, which Bischoff claimed went "rather unsuccessfully from my perspective."
The Thunder program flopped for WCW, as many of the top stars refused to appear on the show. And when the nWo seemingly broke up, Hogan and Nash once again reformed the faction via the infamous Fingerpoke of Doom incident.
WCW's obsession with having the nWo run the show is what led to its rise, but later its downfall. On the WWF side, Vince McMahon changed up the content (going into the Attitude Era), and found ways to replace veteran wrestlers with younger talents.
As such, that's why we just watched the Raw 25th Anniversary Special, and not another episode of Nitro.