There is simply a law of the OOTS world, and really of fantasy in general, that the laws of probability are only suggestions, to be ignored at whim. So when they started to oppose the party, it became mandatory that they be opposites to the party. No effort was required on the part of Nale, and an effort to avoid it would probably have failed.

While much of our information comes from a distinctly unreliable Nale, the given information is that he had no interest or knowledge that Elan was in the area. He was after a piece of magic and got a chance to make a twofer out of it.