Hogan was the catalyst to the NWOs success. Hall and Nash would have never become what they did without Hollywood. Then Goldberg brought WCW to a whole different level with main stream media. Hall was just perfect time, perfect place, and rode the money wave $$$.
They mutually enforced each other. Hogan was growing stale and turning heel was just what the doctor ordered. But it had to be done the perfect way; or it would have flopped.
With WCW giving the impression that "Razor" and "Diesel" were invading its territory while still being part of the WWF, having the WWF's biggest star join this renegade crew made perfect sense.
If Hogan didn't join them, WCW would have done the same-old, same-old, and misused Hall and Nash, just as they did in the past. Hogan would have continued to be stagnant.
If Hall goes but Nash stays, the NWO doesn't take off at all. Nash claimed he finally decided to leave, because Bret Hart wouldn't take his jackknife during the match at "In Your House: Rage in the Cage". He was supposed to hit Hart with it, try to leave the cage, only to have Undertaker drag him underneath. That allowed the Hitman to exit and keep the title. Instead, Diesel delivered a nutshot, prior to his exit attempt. The Diesel-vs-Undertaker match at WM12 didn't have as much steam because of that, according to Nash.
What if Diesel goes but Razor stays? Still no NWO. I've often thought that Razor would have eventually been WWF champion had he not jumped ship. He was too over and eventually, McMahon would want to put the belt on a big man. With Ultimate Warrior's flameout, I don't think he brings back Sid and pushes him, if Razor is still on the roster.