Windows is hard to replace in large organizations. Is there actually any real AI competitors in the stack? Well Google, maybe. The whole Windows+Office+AD+Exchange and now Azure stack is unlikely to go any time soon. However badly they screw it up.

True. Basically any medium to large scale business is reliant on Windows/Office/AD. While there are open source alternatives to Windows/Office, I can't think of a good open source alternative to AD/Group Policy/etc