I agree with the conclusion, but not the logic. A much more likely cause for IE supremacy is an established set of enterprise "web" applications, where these (badly written) "web" applications are so broken outside IE that they might as well be Win32. If executives sank money into applications that now run the business, and find that IE keeps those applications running, they're more likely to establish an easy policy…
No, what I mean is that most enterprises have an ERP system which comes with it's own, quite efficient domain-specific language and development environment, so when they figure out that f.e. they need a system to reserve projectors for presentations, the easiest way is to develop it right inside the ERP system. Or use something similar to these efficient ERP development environments, such as FoxPro.
Why would you put your application on the web when the point isn't to be able to use it from a netcafe, but it is used only by people sitting in an office and keying in data all day long?