What were the motives behind the salesman giving the boys the lightening rod?

Chapter 1 sets an ominous tone for the rest of the novel. The approaching storm signifies the events of the next week that will change the lives of both boys. Tom Fury plays a kind of reluctantly benevolent advisor. He has spent his life walking before storms, and he knows that one is about to arrive. He gives an impression that this one will be particularly nasty. "No ordinary storm.... Yes, bad, here it comes, feel it, way off now, but running fast...," he says as he takes his leave of the boys. The fact that he feels compelled to give away a free lightning rod underscores the danger that he perceives threatening the two boys.