The problem is, those bees moved to that tree as a staging point. they congregate there, and the scouts go out searching for suitable locations. When they find a suitable location, they return and tell the other bees about it by dancing on the cluster.. Other scouts will find other sites, etc, etc, and eventually a decision is made to move into ONE of those locations. usually the location is some distance from the mother hive so that there is less competition, provided of course, that there IS a suitable location further away...
It all comes down to suitability..
if there is no other suitable location for them to go to, they will move into the hive Jen has on her back porch that was readied for her to do a split etc.. That is just my understanding of how it works. Like everything beekeeping, once you think you have it figured, they ruin all that effort by proving you wrong...