The C Tor library was crashing, nobody could figure out why, so they rewrote the dependency in Rust and crossed their fingers. That's not engineering, that's a cargo cult with better type safety.

The Rust evangelism cycle: C code has bugs. Rewrite in Rust. Bugs disappear (because you rewrote it, not because Rust). Declare Rust the savior. Repeat until every dependency is Rust and the compile times are longer than the bug-fixing sessions they replaced.