OK, I'll explain.
How do you get 2 Final Four basketball games in prime time on a Thursday? If you start the first one at 6 eastern and the second at 9 eastern, that's 3 and 6 on the west coast, with everyone who works missing the first game. If you go to 6 and 9 on the west coast, then the games would be at 9 and midnight on the east coast. You can't fit 2 games into prime time on a Thursday and you don't need to on Saturday as people are generally home on Saturday.
Oh and BTW, the NBA schedules games on TNT or ESPN for 7:30 and 10:00 (2.5 hours), but you need an extra half hour because the games are played in the same arena. For the NBA telecasts, they end one game, have a quick interview, and then go directly to the tip of the 2nd game.