Facebook (and Whatsapp, and Instagram) has a truckload of users. I think people would get really mad if they were forced to close shop in Europe. (Not sure that rage would lead anywhere, considering how the EU works...)
I trust Microsoft a little bit more than Google (which is not to say much), and Edge and Chrome are the only reasonable alternatives we have in 2020 for a web browser (now that Brave has been killed in my opinion by a thousand paper cuts)