The majority of that money (FMF) comes from our taxes, goes to Israel, Israel is bound to spend it on arms from American arms companies, the owners (stockholders) of those companies get the profits, cycle some of it back to politicians and lobbyists, etc. So it’s a net gain for the beneficiaries, but a net loss for the rest of the population. It also makes our infrastructure more targeted towards arms production and less for our own needs. There isn’t an additional inflow of money, so that essentially means a net loss.

That’s essentially the broken window fallacy on one hand, and actual redistribution of wealth upwards on the other hand.