The author is also the creator of the textual Python library for creating TUIs. The performance benefits of Rust don't seem very useful in a tool where you spend a few seconds typing in a prompt and then 90% of your time is spent waiting. As long as the UI is responsive when typing there wouldn't be much of a difference.

The creator of Toad, made a TUI framework in Python (Textual). What is so special about Rust, aside from it being blazingly fast and compiled, that you want from it?