Large project uses Rust backend. My backend developer left. How hard is it for me to learn Rust and take over for him.

I've been working on an app for the last 8 months (in Flutter/Dart). I originally was a one-man-show. So, I created the backend in NodeJS. However, as it grew, I recruited some other software engineers. The backend developer I recruited converted the whole (backend) system to Rust for efficiency (he did an amazing job, he's a great guy!). However, he now has to leave for xyz reason.

Would it be possible for me to 'learn' Rust and to work on his backend? I've heard horror stories about how hard Rust is to learn and its syntax. For some context, I'm a solid Flutter developer, with decent experience in Python, NodeJS, NextJS, ReactJS, along with some database systems. However, I've never worked with Rust before - it scares me.

Would it be stupid for me to try to learn Rust quickly and well enough to be able to build on what he's already done? Is learning Rust well enough for this sort of a large project a futile task?

Thanks.