WCW cruiserweight style was incompatible with WWE style
They toned em all down and wanted them to work restholds. They didn't have agents in WCW so they got to steal the show by recklessly throwing splash mountain power bombs mid match. And it was awesome.
To be fair to WWE, they had valid points. The WCW style was going to lead to injury faster, they needed cruiserweights to stay healthy so they could work more dates so they needed to adapt to a safer more boring style.
Also you can't just use a main eventer's finisher mid match. You have to protect spots.
Rey stood out because: he's Mexican American and fluently bilingual. And he was willing to roid.
And he figured out to do less is more with the 619, which is like the people's elbow or the worm. He figured out how to tell stories as a real underdog,
Vince does have a somewhat misguided/somewhat valid belief that there should be one masked wrestler to make them unique. That's true BUT Japan was able to build divisions around solid hands wearing mask gimmicks and being the evil foil for the masked ace. If Vince was more creative, he could have put some of these guys under hoods to be heels against Rey and make even more money.
But he had already Rey merch money so he didn't need to try harder.
