Obviously Microsoft felt bad when they had to kill the old Edge browser that was based on their own HTML rendering engine. Must feel like a second-rate tech company when you can't write some code to render HTML with sufficient quality.
Now they can get back in the game with a 3-word prompt!
And then every time there's some change to web standards, it's just one more prompt where you say "Hey Copilot, take a look at this page that describes the change, and update our browser code to add this!"
It's not that difficult to take an existing mature codebase and morph it such that it looks quite different but is functionally unchanged.
This is a very different task than building something that's not been built before.