Well, if you had massive dependencies you'd probably look at consuming them as shared libraries making your binary smaller than if you rolled your own solution, right?

The fact that the Godot editor includes the Godot runtime along with its own UI- and graphics stack (if I'm not mistaken?) in such a small bundle makes this even more impressive to me.

Godot has many parts besides the UI and graphics stack, and most of its dependencies vendored and statically linked. See the thirdparty folder for a list: https://github.com/godotengine/godot/tree/master/thirdparty

The official binaries include everything, but many of the larger bits are optional and can be disabled during build time to reduce the size of the executable: https://docs.godotengine.org/en/stable/development/compiling...