They just realized they didn't really needed their own rendering engine. It would have been a nice to have, like in the old days of IE6, where they could decid

They just realized they didn't really needed their own rendering engine. It would have been a nice to have, like in the old days of IE6, where they could decide over the direction of the web. But more valuable to them is that people are using a browser they control (no matter the tech within) - which is why they try to push you to edge however they can.