No, it wasn't a mistake. Tazz was a great suplex oriented wrestler, but, honestly, for the style of wrestling he did, he was small. He would have had to completely change his wrestling style, because while he was one of the stronger and most intimidating people in ECW, he would have been undersized in a WWF/E ring. On top of that, he never really had much charisma...he didn't develop any kind of personality until after he got behind the mic as a commentator. If you look at some of the biggest names in the original ECW, Tazz, Raven, Shane Douglas, you don't think "yeah, that guy could be the WWF/E champ, easy..." You see them wrestle similarly sized guys, and they looked impressive, but, in a WWF/E ring, he wouldn't have been the monster he was in ECW. On top of that, his injuries were getting worse, so its possible that by the time he signed with the WWF/E, there simply wasn't enough time left in his career to have a long sustained push...Few people get that huge push their first year or two. Perhaps had the injuries not shortened his career, he might have been given something, but, he just had too many things going against him to justify getting a monster push when he entered the WWF/E.