Severing the connection between Skynet and every single terminator (If at all possible for humans to accomplish simultaneously) would not completely hamper Skynet's functions. Unlike
earlier series terminators, every terminator from series 800 up has been given a neural net [Learning computer] that has an intelligent, self aware AI which can function independently of Skynet's direct control and has factory programming that guides its actions on behalf of Skynet's will. Skynet can still remain in contact with and coordinate its forces via multiple forms of communication including wi-fi, radio waves or audio voice signals.
I believe that the other humans would agree that the humans at the Pentagon who gave total control of the missile defense systems over to Skynet were indeed fools that lead the human race into
Judgement day.