Two words, Internet Explorer
For 25 years, Microsoft pushed the most commonly abused malware engine as Internet Explorer, at its core ActiveX as part of their own dotnet programming languages, ever to be unleashed on the populace, and only then begrudgingly admit to defeat in killing it off having found better adware and tracking in Google's Chrome engine now. Exchange servers are still a constant liability people misuse and abuse, and Active Directory every time remains the common denominator at the heart of most infections due to it's ubiquitous presence in 99% of enterprises today.
If people haven't learned by now to mistrust Microsoft products, they impose their own blissful ignorance.