I'm sure if you looked at "servers installed in a data centre" then it would be closer to what you expect. But there are so many servers doing "boring" jobs in cupboards youll never see it totally skews the figures.
> In 2019, the Windows operating system was used on 72.1 percent of servers worldwide, whilst the Linux operating system accounted for 13.6 percent of servers. Compared to 2018, both companies experienced an increase to their overall market share.
(And since it describes both “Windows” and “Linux” as “companies” that gained marketshare, I’m somewhat suspicious of their information gathering.)
But not being registered with them, I don’t have access to what passes for their detailed source information for that claim.