PowerPoints can be saved as mp4 or mov video files. Here is how it is done.
Keynote slides can be exported as Quicktime files. Here's how https://creativepro.com/export-keynote-presentations-movie/
While Google Slides does not provide an option to save as video, there are a number add-ons that do. https://workspace.google.com/marketplace/app/creator_studio/509621243108