“We are happy to announce that the WineHQ organization will be taking over as the stewards of the Mono Project upstream at wine-mono / Mono · GitLab (winehq.org).”
Microsoft took over Mono when it bought Xamarin in 2016. The last major release was July 2019. Now that its own fork in dotnet/runtime is done, Microsoft hands the original to the Wine team and tells users to migrate to .NET. A donation of a project you stopped shipping five years ago is a cleanup job with a press release.