It is Microsoft's fault. Windows Update should be able to tell you that you're missing a prerequisite. Failing that, it should check to see that it can verify all the signatures before starting the patching process.
Windows Update is a remarkably broken system, as anyone who's ever ended up with a mysteriously corrupted catalog can tell you. (And based on online questions and complaints, this happens a lot.) Or anyone who's ever had it report an "unknown error" with an error code that's straight out of WinError.h; Microsoft's WinUp team apparently can't even be bothered to call FormatMessage.
And Microsoft's handling of updates is crap, issuing vague "this fixes a possible issue with something" updates that lack any useful information.
And then there's the Win10 auto-rebooting, which frankly makes the OS unfit for purpose. (Yes, the "metered connection" workaround can prevent that - until you connect to a different network and forget to enable that setting again, or your organization overrides it with a group policy setting.)
Biting the hand that feeds IT
