Will laughed because he was "acting" and he's a bad actor. That "joke" wasn't worth a laugh. He could have also been a bit nervous knowing what he was getting ready to do: engage in a put on publicity stunt to draw eyeballs. No, just yelling out something about a medical condition would not have drawn 1/100th of the attention. He almost didn't sell it, which is why he started yelling some bullshit he probably heard some other real tough guy say.
And he isn't risking anything, his career is set. He will pay no price, the Academy is just posturing. He will be known as the man who saved the Oscars. So that is what he has to gain from it. He got the eyeballs, and that is really all that matters. The controversy blows over in a week and people remember the slap and think Will was justified and the Oscars is back and the rest (violence and the laughing at and glorification thereof by the hypocrites who preach otherwise) is forgotten because it doesn't fit the narrative.
Will comes out on top, bigger and better.
