Jimmy Johnson is my favorite all-time coach. But let's not forget one simple truth - those early 90s Cowboys teams were just better than anyone else. Jimmy inherited the #1 pick in the draft (Troy), and then pulled off the genius Herschel Walker trade (which brought in Emmitt, Darren Woodson, Russell Maryland and Kevin Smith among a total of what turned into something like 13 total draft picks). Give Jimmy full credit for that. He also coached in the pre-free agency era where players literally could not leave even if they wanted to.
So, yes, give Jimmy credit for being inspirational, giving great speeches, and being a brilliant motivator and tactician. But I think it's short-sighted to attribute that success to him convincing players "to want it more", or to even assume they did want it more. Sometimes raw talent looks a lot like motivation.