That may have been the story, but avoiding paying per-core licensing fees for an operating system is the only sane decision.

Operating systems and other applications that demand per-core licensing fees exist only because the people who buy them do not use their own money for this, so they do not care how much money they are wasting.

Most companies waste huge amounts of money not only for software, but for many other things, because those who have the power to make purchasing decisions have personal interests that are not aligned with what is really optimum for the company, while those who might have the best interests of the company in mind do not have the knowledge that would allow them to evaluate whether such purchasing decisions are correct.

The survival of Windows Server is not justified by any technical advantages. A few such advantages exist, but they do not compensate the huge PITA caused by licensing. I worked at a few companies where Windows Server was used and replacing it with either Linux or FreeBSD was always a great improvement, less by removing the payments for the licensing fees, but by providing complete freedom to make any changes in the environment without the friction caused by the consequences that such changes could have in modified licensing fees.