Answer:
Naïve realism
Explanation:
Naive realism is a state of mind when a person believes the world as he/she sees it. There is no attempt to understand the actual meaning of things. Things are just understood at a surface level.
Here, the coach eats a little grass every time his team is visiting another school's stadium and his team always wins. He makes the connection that his team wins only because he eats grass. So, far his team has not lost this further solidifies this idea in his mind. He does not try to understand the actual reason why his team wins and the other teams lose.