Slapping the host at the Oscars because he made a joke at your expense is like slapping the animal trainer at Seaworld because you got wet. Insult humor targeting the nominees, and also their guests, is part of the ceremony: You accepted it when you decided to attend.
Jada did not need to attend: She could have stayed home and would likely have not become the subject of a joke.
Anyway, I find it telling that Will Smith originally laughed at Chris Rock’s joke: I think his wife, who is intensely controlling and manipulative as can be seen in her constant cheating, probably put him up to it: She likely said something to the effect of "A real man wouldn't let him get away with that." Of course, a real woman can take a joke.
It is certainly bizarre that a man who readily accepts his wife's infidelity must prove his manliness by slapping another man for making a relatively harmless joke about Alopecia---hardly a serious medical condition. If Chris Rock had slept with her, I suppose that would have been okay---perhaps Will would have given him a high five?
Furthermore, Jada Pinkett Smith invited the joke: She made a deliberate display of her baldness in an attempt to garner sympathy. Wigs and various forms of headware are completely acceptable and unremarkable in the black community—indeed, she had worn a beautiful headdress to an awards ceremony not that long ago. She was making a deliberate display of her baldness: She was inviting Chris Rock to make that joke.
It goes without saying that the Academy should—if it is at all possible—take back his award. While I generally oppose cancel culture, you cannot expect to be rewarded for disrupting the very award’s ceremony that is honoring your performance. I don’t believe in punishing people for what they say, but what actions are an entirely different matter.