Best guess, the nitrates were destined for rockets Hezbollah was making to bombard Israel with. The Israelis have made very clear that since Hezbollah has taken over the government, and has cowed any internal opposition with murder and bombings, that they would not stand by while a rocket arsenal was built up to attack them. They would make Hezbollah pay regardless of any blowback. Hezbollah has kept their rocket factories producing weapons and has located them, and their storage buildings, in civilian areas to deter their destruction. With a more Iranian friendly government coming in American, and the political Left/Right divide widening in Israel, Hezbollah is learning that their tactics of using the civilian population as shields is no longer a deterrent. I just hope any reckoning finishes before the election as the current trends are favorable for Iran and Hezbollah. Again, best guesses.