Fedora may be becoming the default for desktops, not for servers (Debian possibly the default for servers).
Fedora is upstream for RHEL, which is absolutely dominant in the server space some sectors that require enterprise support.
Why do you think Debian for servers only ? Did you use Debian SID or Testing as a desktop ?
Actually on servers RHEL is still the default (43% server OS market share), followed by Ubuntu at 34%, Debian at 16% and SuSE at 11%.
https://commandlinux.com/statistics/linux-server-market-shar...