You appear to have some large images embedded in your notes, instead of them being stored in your media folder. If you search for ‘base64’, you can locate them. Do you know how the images got there? Did you add them using one of the Anki clients, or were they from a shared deck?
After you’ve identified them, you should be able to use this add-on to move them to your media folder, and then check database should shrink your collection down.