Not just volatility but also flip-flopping. Rust was explicitly a contender when they decided to go with Swift 18 months ago, and they've already done a 180 on it despite the language being more or less the same as it was.
For the Ladybird project, now is the best time to be making a big decision like this, and it's commendable that the project lead was honest to recognize when an earlier attempt was not working, to be able to re-think and come to a better decision. I'm no fan of Rust, but for this project I think most of us would agree it's a better language than Swift for their purpose.
I've seen another team doing something similar, they went through endless rewrite cycles of a major package but never shipped, and eventually the project was axed when they proposed to do it all over again, but this time even better.
https://github.com/LadybirdBrowser/ladybird/tree/8017f8a7ed3...
The core browser engine, JS/CSS/layout etc will always be original.