When it came down to it Waterford didn't or couldn't match Cork's workrate. Cork gambled on off the ball runs and on abandoning their posts to hunt down ball carriers all day. Waterford didn't, and they weren't as prepared to rescue one of their own men in trouble as Cork were.
It's no coincidence that the two form teams in the country in Galway and Cork are the two with the best workrate and, on the face of it, conditioning. That counts for a lot in June. Whether or not it'll still be decisive in July and August remains to be seen.