Seems to me self evident, however, that if perhaps 400 of the Fortune 500 profit from war, that a big objection TO war is eliminated.
I doubt if any arms makers are sitting around saying, "You know, if the U.S. engages in an effort to kill and maim 10s of thousands of people with our weapons, we make more money, so let's lobby for war!" But neither will the big arms makers spend any money lobbying against war. It's not in their interests to oppose a full scale invasion of, say, Iran. And if doing so means a few extra $billions in profits, human nature as it is will dictate that arguments for war might take on a more favorable tint. Furthermore, those individuals who are inherently "hawkish" in their outlook on national defense would tend to take senior level positions with arms makers. Not going to have a peace activist rise to the senior ranks of the big defense companies. More likely is those ranks would be filled with former military than hippies from the 60s and 70s. So interests and profits will naturally align. Hawkish politicians get support from defense companies, providing another incentive, whether that is merely a self reinforcing cycle or corrupt or sinister doesn't really matter.