I feel like most explanations are overcomplicating it.
By the rules of the game, the option of switching is asking you the question "Do you think you chose the correct door out of the three?". If you think you did, you don't switch. If you think you didn't, by rules of the game, switching will get you to the right door. Since you had a 33.3% chance to choose correctly and 66.6% to choose incorrectly, betting against yourself and switching is probably the correct choice.
By the rules of the game, the option of switching is asking you the question "Do you think you chose the correct door out of the three?". If you think you did, you don't switch. If you think you didn't, by rules of the game, switching will get you to the right door. Since you had a 33.3% chance to choose correctly and 66.6% to choose incorrectly, betting against yourself and switching is probably the correct choice.