It bothers me that no one explain the Monty Hall Solution easily.
If you don’t know the Monty Hall here is a link to read on it:

Monty Hall problem - Wikipedia
The easiest way to make someone understand why switching puts them at an advantage is to change the situation.
Instead of saying there are 3 doors, say you have a 100 doors, and you pick one, then the host opens 98 doors with goats and asks you:
Would you care to change your answer?
Yes!