NWO doesn't work without Hogan. It brought fans back to wrestling which was suffering in popularity. WCW was sold because of the Time/Warner merger.
The invasion angle was working fine without Hogan.
Did Hogan going bad make it better?
Absolutely.
It also was part of what caused so many problems down the line.
Look at how much they fucked up the Sting match.
Did the NWO getting red hot help wrestling?
Absolutely.
WCW was sold as part of the merger, yes, but it had been dying for a while once WWE took over the Monday Night Wars.