Mac gave them what they needed in 1991, enthusiasm, a few thrilling wins and a team that was as enjoyable you will find for a 6 win team. His 1992 season was atrocious.
Parcells took a nuclear bomb to the entire roster and blew everyone out essentially. Parcells won with his Giants guys coming up and having the chance to draft Bledsoe.
Mac to me, if given the right team, would have been successful in the NFL. He was the 1980s version of Pete Carroll. However, he wasn't gonna be one of those turnaround experts like Parcells.