What we have is Big Teams not advancing to the final stages due to something? I really haven't tried to understand conference size, depth and coaching to try to get a grasp on how many tough games the Big has twice a week. Typically, the Big is deep making for many tough games with good coaching Road games historically have been tough and a key to winning the Big. Why the Big hasn't fared as well considering going far in the tourney can have many speculations as to why.
Was the Big prepared as far as knowing how to execute against various types of play...AND did the Big have the personnel to execute what was needed? If not, then what happened to alter before and after conference results against variety of styles? Only explanation I could come up with is habits...months after preseason gets teams locked into some habit that somehow makes playing styles previously successful against now not as successful either due to the Big Teams for not seeing it enough or the other teams getting much better at what they do?
The other thought is that the Big is prepared for other approaches, but the grueling season takes a toll not just physically, but mentally, and the teams are worn down at the end of the season and as you say...the Big Tourney makes it even worse by being so close to playing the NCAA tourney. Does the physical play allowed make it worse for teams to advance in the tourney? No idea, but personally I think the whistle changes. The big allows more physical shoving and pushing by the bigs it seems. Big players in the Big don't find the same number of scrapes, digs and overall quick slaps as is allowed in the tourney I don't think. I see more of this I "believe" in the Big East as well. Perhaps a different whistle adds to the speculation? Granted some of those Big refs that are more common faces in the Big end up doing tourney games...but perhaps not as much with the same group of partners they normally work with in the Big. Lot of speculation, but for me it isn't thinking the Big teams were not good enough...