Why Did the Nazgul Wait at Crickhollow?

[littlemanpoet]

There was a faint stir in the leaves, and a cock crowed far away. The cold hour before dawn was passing. The figure by the door moved. In the dark without moon or stars a drawn blade gleamed, as if a chill light had been unsheathed. There was a blow, soft but heavy, and the door shuddered.

It was the hour before dawn that the black riders entered the house, regardless of when Fatty Bolger's escape happened. Though I would find it almost as puzzling that they did not hear him flee out the other door, except that elsewhere we learn that the black riders' senses are compromised by their state of existence.

Perhaps there was a plan amongst all the black riders to strike simultaneously. Perhaps the three black riders at Crickhollow did not "smell" the Ring, and were uncertain because of it. Perhaps they were suffering from overconfidence and wanted their prey to experience the terrors of the night before they attacked. These are all conjectures, but I'm not sure a more definitive answer can be had.