Remember 20 years ago, when .NET wasn't just a managed software development platform? It was a company-wide strategy[1] that was meant to encompass more-or-less their entire product line. The whole Microsoft future was .NET, and they were going to have a .NET edition of Windows, SQL Server, Exchange, etc.
Since then, those plans have been dropped, Microsoft's (.NET-based) preferred GUI toolkits, WinForms and WPF, were replaced by one that is .NET-compatible but not .NET-native, etc. etc. .NET just isn't as central to Microsoft's identity as it was 20 years ago.
Which, I'm guessing, means that the .NET team is now a lot freer to go cross-platform without inviting the wrath of the Windows team.