If the Triple Crown was a movie script, then the Kentucky Derby would serve as the explosive first act. The true intent is to introduce the main characters and establish the storylines in a fashion that hooks the audience.
If the second act (The Preakness) builds up the storyline then by the time the third act (The Belmont) starts, the drama is at its peak level heading into the big finish. If the Derby winner doesn't go on to take the Preakness, then it becomes an M. Night Shyamalan movie...one that people will try to convince you still has some suspense, but we all know that no one is watching anymore.
Since 1978, we have had 11 storylines that kept us captivated all the way to the end. All 11 had unhappy endings.