Well, the lucha boom happened in 1994 with AAA, when all of those guys you mentioned plus a few others were young and coming up at the same time. So WCW took a chance on something that was hot, and those guys were super talented and it worked. Mostly because WCW let them work their style.
WWE tried to copy, not many people remember, but they had the Super Astros show that bombed, because they filmed it in front of RAW crowds at tapings in front of people who didn't treat them like stars because they didn't now who they were. So of course, "they cant work", etc. This is Vince we're talking about, so forget just letting them work their style. He wanted to unmask El Hijo Del Santo, for fucks sake. Talk about not understanding the culture.
And remember, it took Rey a while to get into the WWE. It took Vince YEARS to accept the fact he was a legit star, even when he was drawing money for him. But you are talking about a guy who is elite level charisma & talent, who is an American who speaks English and understands American style wrestling psychology.
So when guys come from Mexico now, they have a million things working against them. The psychology is massively different. Turn on lucha one weekend and watch for a few minutes. The way they sell, everything is different. Plus they work the right side of the body, and in the rest of the world you work the left side. So that's a big switch, you have to unlearn years of habits. Plus, if you don't speak English, forget it. Another massive barrier. How many Mexicans succeded since Mil Mascaras while not speaking English? Psicosis? Only because he was Rey's base. La Parka is a god dam charisma machine and a legit mega star in Mexico, and he couldn't even get any traction here.