How? All he knows for sure is the prez did something, and that much should be taken for granted after his friends had outright told him beforehand that the guy was cheating.
Because fuck them that's why.
I don't remember the exact logic to this, I think it's explained later but I'm not sure. I think it made sense.
The narrator is full of shit, BTW. "They can hardly be blamed (for misunderstanding)" my ass.