Most of the leaders are powerless and are just going with the flow. Even if they do care they can't do anything. No use getting mad at them really.
When you get notice you are laid off, you are done. Do not go to meetings or standups with the team and polite-fully decline and clear your calendar. What is 3 weeks going to do anyway? Meet the expectations outlined in your severance documents, answer emails and requests from management and HR, that's it. Refer other requests and questions to your team or manager. You will win no points or favor for being a good sport or holding your head up high like I see in these Linkedin posts. If you want to take any pride in yourself, move on and do not give them any more of your energy.