No, I don't understand it, but I'm taking the word of people described in the media as experts. I imagine you are taking the word of different experts. Maybe yours are right, maybe mine are.

"In the Iraqi arsenal, a warhead is a warhead - an empty ordnance space strapped to a missile. What matters is the payload, be it explosive or chemical or nuclear. The item placed in the warhead denotes the designation. These warheads were stone-cold empty, so by definition they are not 'chemical warheads.' They are, in fact, nothing, because they were loaded with no payload. Furthermore, the word 'warhead' is in itself misleading, as these were artillery munitions." (William Rivers Pitt - Author "War on Iraq")

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There is a big difference between having a few nuclear weapons

I don't think anyone seriously thought that Saddam had any nuclear weapons. I don't think anyone even claimed that he did (which isn't the same thing). The stories (punctured fairly quickly) were about his supposedly having had people going around trying to get the ingredients together to cook some up.   And nuclear weapons are pretty useless for fighting an invasion, and they aren't even any use as a deterrent unless you've got a method for delivery.(Such as having them, installed in your embassy basements in your enemies' capital cities.)

The more plausible claims were about chemical weapons, which he had used, and which would have had a devastating effect on a ground invasion force.