wtf is this

indeed it is

I don't get it D:

if you stay with your original door you have a 1/3 chances of winning the car
but if you switch, the probability of opening he door with the car... is 2/3... so it is in your favor to switch

How does switching to a different door increase your chances by a third when there's still the same amount of doors to open?
At first it's 1/3
If he opens one and it's not the car then there's 1/2 that the one you have is right, if you switch, still 1/2

What am I missing?

because there is still 3 doors, regardless if one is already open
since you know already whats behind door number 3... door number 2+3 is now a 66% chance of having the car inside

here's some pics to explain it a little better

yes, you should switch. it takes some getting your head around it, but look at it this way.

say you pick a door. statistically, in 2/3 cases you will have picked the wrong door. 1/3 times you will have picked the correct door. so since you pick the wrong door 2/3 times, that means in 2/3rds of all cases it will be beneficial for you to swap. hence why you have a 66% chance of winning by switching, and only 33% chance if you don't switch.