Goldberg never stood a chance. Putting him against the Rock and Chris Jericho (two of the best mouths in wrestling history) and having them destroy him on the mic derailed him before he even got going and marked him as "uncool". Even though he won against both of them, it wasn't enough to wipe all the egg off his face after they got done with him.
As for Brock, I fully believe Vince planned for him to be the guy they would build the post-Attitude Era WWE around (Brock would lead SD, with HHH leading Raw). He had it all: he was a big powerhouse of a guy and he could go in the ring, plus he had heat magnet Paul Heyman as his mouthpiece the first year. The only problem was he hated the constant travel and notoriety that comes with being a WWE star, so he walked in 2004. When he walked, he was only in the second year of a 10-year deal. Who knows how much he could have done if he had stayed.