This is mainly for keeping Internet history accessible. Flash had tons of problems, but a lot of amazing content was created on the platform. Now that it's gone, it's difficult or impossible to access the historical content.

I don't expect anyone to be making new flash content, but I'm really excited that all this work is going in to make sure we don't lose a really cool slice of Internet history

It's done in wasm, so we have a much bigger problem if it does.

No, WASM was specifically designed to allow running native-like code without any of the security issues that plugins like Flash had