https://www.techradar.com/news/is-chromium-based-edge-the-best-thing-ever-to-happen-to-googles-chrome-browser

At the end of 2018, Microsoft officially announced that the old Windows 10-only version of Edge was dead, to be replaced by a revamped spin on the browser based on Chromium – the same rendering engine which Google’s Chrome browser uses (and some other efforts besides, such as Opera and Vivaldi).

Edge’s browser market share was pitifully small (and indeed starting to go backwards), so Microsoft had to take action in some manner. Quite drastic action, really, but Microsoft needed to move quickly to stop the rot, and Chromium evidently seemed the ideal way to ensure better compatibility with websites for the new Edge, and make it more reliable overall.