The monuments bundle contains zero monuments

Rust ships its prefabs as Unity asset bundles, so the obvious move is to open monuments.bundle and read the prefabs out. There are none. Not hidden, not compressed oddly. The file contains zero objects of that type.

Monuments are asset scenes. The geometry is there, but it is laid out as scene hierarchies with the actual mesh references spread across other bundles, and the textures are external pointers into a separate archive that you have to open simultaneously or everything resolves to grey.

This is the kind of thing that costs a week because every individual step looks like it worked. The bundle opens. The objects parse. You get meshes with plausible vertex counts. They are just the wrong meshes, and nothing tells you.