The thing is a lot of scientists are going to have to learn FE technologies eventually. The push to make scientific work more presentable and accessible means JS' place in academia is cemented for a long time.
WebAssembly is still a long way off and given that even Rust WASM was found to usually do worse than JS, I highly doubt Python WASM will outperform it any time soon. Even once it does become worth it, tooling has a long ways to go
> people would rather write Python for ~accomplishing the task they set out to~ than have to muck around with another language entirely.
your argument seems to boil down to: people know Python so they wanna use Python. People can just as easily know JS/TS. If I'm a botanist and I really don't wanna invest too much of my time in learning languages I can choose between Python, the language with all the scientific libraries, and JavaScript, the language of the web. If I choose the former, I'll likely have to bother someone to help me present my work to the web anyways. If in the near future JS also reaches good support for scientific/ml libraries it seems like entering that ecosystem is an obvious advantage. I get to learn the web and access scientific libraries at the same time
Also I don't really find Python all that legible. The language you're describing isn't Python nor JavaScript. It's something like Ruby. Modern javascript has some obvious advantages when it comes to syntactic sugar like arrow functions. It's also easier to teach because you don't need to install anything. Just open up your html file in any browser