Rust & cargo do more than just compile. For example, it basically has buit-in ccache.

It is also easier to split large libraries into multiple crates, though an average project still uses more libraries than an equivalent C project. I wouldn't be surprised if the "AI" also pulled in more libraries than needed, or has unnecessary library features enabled. I'm pretty sure that a cargo plugin for pruning unused libraries was featured on the rust blog, as a featured third-party plugin for a cargo release.