Decline is usually inexorable; that's what a decline is.
WCW declined inexorably because literally everything was wrong with it. This is a company that paid astronomical sums of money for Hulk Hogan to suck himself off onscreen, and this was likely literally the case for Lanny Poffo off it, who was paid a six-figure salary to do absolutely nothing. Literally nothing - and he was still of more value to the promotion that many of the top stars used to pay for their swimming pools.
By 2000, WCW was a grotesque, inexplicable WWF lite that had the good grace, at least, to take sh*ts and immediately flush them as they swerved around the bowl. A constant two-hour head-f*ck, Jamie Kellner, CEO of Turner Broadcasting, smashed it against the wall and through a novelty basketball hoop like the limp, dead hamster that it was.
WCCW, notwithstanding its Weekend at Bernies revamp alongside the AWA and CWA - all roles were played by Terry Kiser - died because all of the old territories were fated to die. Moreover, the company had destroyed its bond with the fiercely loyal fanbase by fictionalising the tragedy that had struck it throughout the mid 1980s.
Sometimes they come back - but sometimes, dead is better...