I think it primarily just worked as the straw that broke the camel's back. It wasn't so much that people thought that the episode was bad, it was that coming after everything else (and in the wake of 9/11, and just around the time that spoilers for Seeing Red leaked) it just got too damn bleak for people to handle.

The shows that were far and away the most successful that year were comfort-food comedies like Friends, which was one of the few shows to gain audience.