Siegel misses the key ingredient. High pressure areas North of the storm held the storm in place. Absent those high pressure areas, the storm would have naturally continued into the US landmass and dissipated itself.
It was being stalled in a location where the storm was able to continue to draw moisture from the gulf and dump it onto the land that produced the incredible total rainfall.
Even I was able to find that out, and I am a total amateur in this area. And so is Siegel just an amateur when away from his area of expertise. He just parrots the obligatory “and yes, global warming played a role” of those who have made a religion out of manmade global warming, wherein every weather event has to be connected somehow to humans burning fossil fuels.
There were many category five hurricanes and cyclones long before there was any significant human burning of fossil fuels. Cripes, Siegel, stick to what you know.