A smart person is the first person to admit when they don't know something. It's a common trait with narcissist to just intentionally make stuff up when they don't know the answer. I had a co-worker who would just guess on an answer for a customer then look it up.

He said it was better to just give them an answer right away even if it's wrong and then call them back with the right answer. He had an ego the size of The Burj khalifa