Make sure to filter by memory instead of disk size
Also that’s not an “almost empty” map, there are a lot of dependencies there, even if they seem small.
The numbers shown in the Size Map menu are orientative, not an absolute number, it’s usually more. Specially if you have particles or anything doing real-time calculations in the editor.
Also check plugins you may have installed, things you have in constructors and automated actions happening on load.
You can try making a copy of the map and deleting everything to see if there’s something in your map that consumes a lot of RAM. If that’s the case add elements back one by one and see which one is consuming the most RAM.