Ohh got it, you are right.

'LONG LIVE THE KING': Donald Trump Gloats After Killing Major NYC Initiative. Trump's administration is revoking approval for New York City's congestion pricing plan, which is raising money to upgrade the subway system

Huffington Post didn't make that statement in this article. They quoted Trump as saying that, by referencing his tweet.

I think trump believed the post. I think he believed a random internet post more than the fact checker. Maybe he keeps saying nonsense because he believes it, and not always because he is trying to manipulate people.