it is not like Bing would cease to exist. Would just have a different corporate ownership.
Think of it from the perspective of the owners of Microsoft, the large shareholders. If Bing is sold to another corporation that these owners also have a large stake in what is the difference to them? They still own both the MSFT OS company and the Bing search company. And the Bing company now has a management team that is entirely focused and accountable to Bing.
Arguably this is also good for users in that their Windows OS now can be more search agnostic. Would be terrific if Bing was not favored in the users choice of search engine. Bing is too ad laden and not focused enough on the actual search to be something I prefer to use.