I do think his performances hurt, he was flat and didn't rise to the occasion - but ordinarily you'd hope a candidate as sensible as Walker would get a chance to stick around and iron out his message, his performance, etc. But he gets no real second chance - the likes of Trump has sucked the air out of the room for possibly good candidates who don't yet have a strong national campaign apparatus.
Walker had an impressive resume, and it was in a blue state. But he got pushed to the margin quickly by Trump and the GOP base, which increasingly looks more interested in reality television theatrics and vacuous one-liners than experience.
He may not have been The One, but I think everyone would have benefited from him being able to go deeper into the primaries. Shame.