Environment:
Windows 10 Home SL x64

Case:
I bought new Laptop with Ryzen processor with architecture x64 and tried to install SharePoint Designer 2013. I thought this issue cause my processor not supported SharePoint Designer 2013, in this issue mention about "processorArchitecture=MSIL", see below image and check solutions.

Solutions:
You know, when you bought new laptop with Windows 10 operating system and also you got pre-installed Office 365. That's the problem, i don't even know the specific root cause. I just tried to clean uninstall all of them using cmdlets.

For example:
I want to remove Word, below cmdlets using Power-Shell (Run as Administrator):

Get-AppXPackage –Name *word* | Remove-AppXPackage

Then, tried to Restart your Windows and re-install your SharePoint Designer 2013.
Hope this helpful :)


Reference:
TechNet Forum