Just search it on youtube.
I discovered this a couple of years ago. The key is that Monty KNOWS which door the prize is behind, otherwise the odds don’t change. It’s complicated, but does actually make sense once you really look at it.
What’s weird is that if Monty were to give this choice every week, no matter what, then the odds would be as expected. But because he didn’t, well...
Monty, the consummate showman, passed away just a few days ago...................
Rest in piece, Monty. Do you pick casket #1, #2 or #3?..............
https://en.wikipedia.org/wiki/Monty_Hall
Monty’s knowledge has nothing to do with it. And he did offer every week. It’s just one of those really weird math puzzles, because there’s a 2/3 chance you’re wrong on the first guess switching improves your odds. It’s deep math I can almost understand but not explain.