Think of an app like SharePoint as "Linux Kernel + Drivers + Userspace tools". There's a few large monolithic executables some tens of megabytes in size for each of the core web apps and services, and then hundreds file format converter plugins, database drivers, etc, etc...

Chromium is similar. It's practically an operating system now, it even has USB drivers! I had to compile Chromium from scratch once, for which I spun up a 120-core cloud VM with 456 GB of memory so that it wouldn't take all day.

With Rust... that would take all week even on that box.