Chromium is everywhere. Microsoft Edge is using it, Chrome is using it. That’s a huge percentage of the browser market. In 2019 the Manifest V3 ball started rolling, quickly. This update proposed by Google to make extensions ‘safer’. Yeah that’s a problem, and why not take a problem and make it profitable? So delicately as Google is they proposed an updated Manifest solution for Chromium. Microsoft could support this proposal or not. And now they’ve decided to support it. Why, is a mystery.
There’s a good article here: