The host knows where the prize is and always reveals an unchosen losing door. That information makes switching valuable.
Your first choice is wrong in two out of three cases. The informed host removes the other losing door, so switching wins exactly when your first choice was wrong. The host always offers a switch and chooses randomly when two losing doors are available. Both strategies are compared on the same simulated games.
A host who sometimes reveals the prize is a different probability model.
The informed host always opens an unchosen losing door and always offers a switch. The two strategies are evaluated on the same games.