Mark, the reason is that the GOPe candidate always wrapped it up after Super Tuesday, or shortly after, so that the actual delegate selection process was pro forma, it didn't really matter.
In previous years, many of the state primaries were held late in spring. That included most of the southern states.
This year, they balked and got moved to early March. It DID make a massive difference.
Yes, and we didn't have bitter clings hold on forever, either. In past elections, the fringe candidates had their funding dry up and they dropped out, pushing the leader to an early win. This time, the fringe candidates are being funded to stay in the race to drag it out.
-PJ