It said outright that the Zuni rocket was from an F-4 across the deck hitting a fuel tank in the ready A-4s.
McCain was armed with very old 500 lb bombs (WWII vintage bought back from the Philippine military) that would not have met contemporary safety standards. Dropped or not, their cookoff time was very short.
The official accident report cited a weapons system safety violation by the deck ordnance crews where they connected the pylon connectors prior to spotting the F-4 to the deck location specified by SOPs. The connection allowed a transient voltage to fire the Zuni.
If armed on the catapault just before launch as specified in the procedures, the Zuni would have had clear way down the deck and into the sea.
There is absolutely no credence to the "wet start" scenario that conspirators love to talk about.