Different sizes of animation clip in file explorer and inspector

I have a fbx file with an included animation. The animation is quite complex since I baked a physics animation with thousands of moving objects in it. The fbx is around 11Mb big. When I extract that animation in Unity with CTRL + D it is suddenly over 700Mb big (according to my file explorer). Though in the Unity inspector, the animation is “only” around 100Mb big. Why is the file size different in the inspector and in the file explorer? And why is the animation file so big in the first place when the fbx file with the included animation is much smaller?