Knowing specific things makes you well-read or perhaps even well-travelled, but it doesn't make you smart.
Being able to utilize critical thinking to break down whats in front of you is what I would consider smart.
For example, a person is not smart for merely understanding how something works.
But a person that does not understand how something works but can deduce or determine how it works over time based on analyzation and critical thinking, thats a smart person.
Thats why scientists in horror movies always die. They aren't very smart, they are just well-studied in a particular field. But despite their PHD they don't grasp that the alien with the red eyes drooling acid isn't there to make peaceful contact.