Class Not Registered

[twhall-umich]

I had successfully built and run the NativeXamlIslands.sln in Visual Studio 2019. Trying to investigate why my attempted modification fails. I used "Manage NuGet Packages for Solution" to update a few of the packages to the latest versions (as in my modified copy of the sample), and now this unmodified original crashes with winrt::hresult_class_not_registered. The only thing I changed here was to update the NuGet packages to the latest versions:

Exception thrown at 0x00007FFDBD27A859 in SampleCppApp.exe: Microsoft C++ exception: winrt::hresult_class_not_registered at memory location 0x000000C80E11CF08.
Exception thrown at 0x00007FFDBD27A859 in SampleCppApp.exe: Microsoft C++ exception: [rethrow] at memory location 0x0000000000000000.
Exception thrown at 0x00007FFDBD27A859 (KernelBase.dll) in SampleCppApp.exe: WinRT originate error - 0x802B000A : 'Cannot create instance of type 'Microsoft.UI.Xaml.Controls.XamlControlsResources' [Line: 13 Position: 32]'.
Unhandled exception at 0x00007FFDAA312EC0 (Windows.UI.Xaml.dll) in SampleCppApp.exe: 0xC000027B: An application-internal exception has occurred (parameters: 0x000002797F19C9E0, 0x0000000000000002).

Prior to that, there was this, but the application marched on until hitting the above. No idea if this is relevant:

...
'SampleCppApp.exe' (Win32): Loaded 'C:\Windows\System32\propsys.dll'. 
Exception thrown at 0x00007FFDBD27A859 (KernelBase.dll) in SampleCppApp.exe: 0x40080202: WinRT transform error (parameters: 0x000000008000000B, 0x0000000080070490, 0x0000000000000014, 0x000000C80E11DD50).
'SampleCppApp.exe' (Win32): Loaded 'C:\Windows\System32\UiaManager.dll'. 
...

[twhall-umich]

I grabbed a clean clone, re-applied the NuGet updates, and now it works again. I am mystified.