Napolitano ought not to matter. He's just a face on tv.
The US intelligence agencies have clearly told the house and senate committees the wire tapping claims are nonsense.
Trump was originally passing along a conspiracy theory from Breitbart because he's gullible. But he was in a position to check the truth of the story. He didn't. So this converts gossip to lie status. He would have shared his evidence with the house and senate himself if there was any evidence supporting the claim.
GCHQ is just the latest defence of the original lie after he realised the US intelligence agencies had revealed the truth. There was no wire tap. The latest defence is no better than the original claim. It's a lie heaped upon a lie.
The real issue is that Trump's a serial liar who will do anything to avoid admitting it. Including damaging the US' relationships with its allies. Crazy stuff.
At this point, I presume he is lying about everything he ever talks about. It will be a nice surprise if he tells the truth one day.