I imagine that especially for a command line utility you also gained an easier deployment story when using rust, given the static linking and lack of interpreter. Requiring PHP to be installed to use a tool has caused me issues, especially with some of the recent PHP 8 updates introducing breaking changes. It’s a better story for PHP on a server where it’s more centrally managed.
The deployment story of the PHP tool in question is pretty good thanks to the semi-official Composer package management system (it hasn't been officially endorsed, but everybody uses it).
People just run `composer install --dev vimeo/psalm` and it works. It can also run on any web server that runs PHP, so I have it running on psalm.dev
OfC the Rust equivalent is very easy to package, and also runs reliably in the browser via WASM (currently ~1.5MB compressed).
