The most interesting thing to me about this story is the long, wandering path Microsoft took to bring a browser back to the Mac after 15 years of absence from the platform.
Once upon a time, Microsoft released Internet Explorer 5 for the Mac, which was widely regarded as the best web browser (at the time) for any platform. It had a great UI, it was fast, and it had great support for new (at the time) technologies like CSS and transparent PNGs. Then Apple released Safari for the Mac, based on the KHTML rendering engine which Apple adopted and called WebKit. Soon after that, Microsoft quit developing IE for the Mac. Also after that, Google used WebKit as the basis for its new browser, Chrome. As with Apple, once their own branch of code diverged enough, they made it their own and renamed it Blink. They also have an open-source browser based on this engine called Chromium. (Also along the way, Microsoft changed from Internet Explorer to Edge.) And now Microsoft will make a browser based on Chromium and it will be available on the Mac for the first time in 15 years.
So IE left the Mac, and Safari led to Chrome, which is now being used by Microsoft, and IE's successor will come back to the Mac.