Obviously the big two straight up lifted a lot of the hardcore stuff, the faked shoots, using actual/better music, mixing up styles from mexico and japan and mma all off ecw and just toned it down slightly, gave it more glamour.
But the weirdest bit was ecw interwove every single storyline they had - they all linked to each other in strange ways (as evidenced in the vid above) almost like an actual soap opera. Don’t think even lucha underground does that these days, it was bizarre. Effective though.