It simply baffles my mind anyone would think it necessary to drop a 150 two to nine megaton nuclear warheads on a single city, especially when part of the mission is simply crowd control. If they survived the first 20 two megaton warhead that is 140× the yield of the Hiroshima bomb that the next 130 would be kinda unnecessary but hell we had a few extra thousand on deck so why not?
There is no overkill when the stakes are of an existential nature. Some of the bombs might not reach their targets. The more bombs, the more that will make it through whatever defenses have been prepared.
Consider that the US constructed around seventy thousand nuclear weapons in total, over the course of the Cold War. Reason and civilized norms no longer apply when your goal is the extermination of a country's entire population. Gotta kill em all.