When you picked your original door, you had a 1% (1 in 100) chance of picking the winner. Consider the 99% cases that you got the original choice wrong. Then t

When you picked your original door, you had a 1% (1 in 100) chance of picking the winner. Consider the 99% cases that you got the original choice wrong. Then the host has no choice, he must close all doors but the winner. So 99% of the time, the host is forced to leave you the winning door. The other 1% of the time, you chose the winner, so the host can do whatever he likes. But 99% of the time (99% of the times you play this game) the host is going to be obligated to close all but the winning door.