It doesn't really come as a total surprise as Silverlight hasn't received any feature updates in quite some time. Internet Explorer 11 will continue to provide legacy support on Windows 10 and the Silverlight framework will receive mainstream support until December 2021.
Support for ActiveX has been discontinued in Microsoft Edge, and that includes removing support for Silverlight. The reasons for this have been discussed in previous blogs and include the emergence of viable and secure media solutions based on HTML5 extensions. Microsoft continues to support Silverlight, and Silverlight out-of-browser apps can continue to use it. Silverlight will also continue to be supported in Internet Explorer 11, so sites continue to have Silverlight options in Windows 10. At the same time, we encourage companies that are using Silverlight for media to begin the transition to DASH/MSE/CENC/EME based designs and to follow a single, DRM-interoperable encoding work flow enabled by CENC. This represents the most broadly interoperable solution across browsers, platforms, content and devices going forward.