I don’t think this is true at all. I see a couple of very obvious reason that large organisations go with Azure.
1) Most large orgs already have Exchange/AD/SharePoint infrastructure. Move that into the cloud and boom, you’re already an Azure customer whether you noticed it or not. Want to take some more IaaS services on? Want a cloud SCM?... Don’t worry about procurement, you’re already a customer.
2) Procurement decisions in large organisations have to satisfy a lot of different stakeholders. A big, reputable vendor, that can solve a huge number of your problems all at once is remarkably attractive to such an organisation. Azure doesn’t have the same features as AWS, but that doesn’t matter. Most of the decision makers don’t care, and the technical teams aren’t likely to use the fancy AWS services anyhow. Forklifting their infrastructure into the cloud was a enough effort to begin with.
This model is very common in enterprise software/services. Symantec and Cisco are other examples of a companies exploiting the same dynamics. Their products are mostly garbage, they go around acquiring other products, and then poorly incorporating them into their portfolio. But they have a large market share to sell new things into, and when they’re talking to their customers they can pitch “just buy all of our products, and that’s like 80% of your compliance worries solved. No need to deal with 10 vendors”.