I had the same problem while trying to install or uninstall CUDA toolkit 12.8. Seems to be related to this problem, which is a known, yet unresolved issue.
I suppose you have Visual Studio installed. While the setup hangs at this activity, a devenv.exe process should appear in your taskmanager, in the details section. This is Visual Studio being launched and trying to configure Nsight Visual Studio Edition. You can kill this process in ordner to make the uninstallation process continue. However, this is only a not really satisfying workaround solution while we wait for Nvidia to fix known compatibility issues between the CUDA toolkit and up-to-date Visual Studio versions.