It's more that it uses concurrency intelligently. The underlying stuff is similar to GNU grep.

ripgrep's README has this to say about speed:

> ripgrep is built on top of Rust's regex engine. Rust's regex engine uses finite automata, SIMD and aggressive literal optimizations to make searching very fast. Rust's regex library also maintains performance with full Unicode support by building UTF-8 decoding directly into its deterministic finite automaton engine.

The author said in a sister thread[1] that for similar tasks the performance is comparable. ripgrep (and ag) both feel incredibly fast because they skip whole files and directories which are usually unwanted when searching.

[1]: https://news.ycombinator.com/item?id=19523263

Worth mentioning that the main author of ripgrep is also the main author of Rust's regex library, so their development nicely complements each other.