ALSO: if you rewatch, you can see that the show's producers are filling in the recipients while the speeches are going on. Horowitz & the other bald guy absolutely know they did not win. Watch 'em in the background.
Here's some shady shit: The other bald guy goes up and starts delivering his speech ANYWAY. He starts his speech knowing they didn't win, that the wrong envelope got read, and it's only after Horowitz starts taking control that he gives it up and is like "We lost, by the way."
Crazy. Like, he was just sorta gambling that... what, the Academy would just let it rock?