Because he literally can't keep his lies straight for two minutes
It was such a Dadaistic shitshow, in fact, that one exchange, which would have generated banner headlines if the AP had been talking to a normal person — like, say, Shia LaBeouf — kind of flew under the radar.
Here it is:
TRUMP: OK. The one thing I've learned to do that I never thought I had the ability to do. I don't watch CNN anymore.
AP: You just said you did.
TRUMP: No. No, I, if I'm passing it, what did I just say (inaudible)?
AP: You just said —
TRUMP: Where? Where?
AP: Two minutes ago.