And they also got Derby to the semi-finals as well. The key was Clough's expert motivation of relatively mediocre players, an attribute that could well have won England the World Cup.
I would argue the old European Cup was harder to win as well. Not only did you need to win your league to qualify you had to win tie after tie. These days if you're a big team it's easier.... you only have to finish near the top of your domestic league to qualify and you only have to finish in the top two of a seeded group to get to the last bit.