Servers have much fewer attack vectors.

Do you really think that a typical scenario of Windows infection is some kind of RCE in the OS? No, that's extremely rare.

Most of malware doesn't exploit any vulnerabilities in the OS. Either a user downloads and runs an infected executable, or they get infected through a bug somewhere in userland (e.g. web browser or image viewer).

Linux server malware is common, mainly targeting naive owners for misconfiguration (SSH password guessing), or targeting remote shell exploits in various popular packages (personally had it happen with Gitlab, for example).

The opportunistic attackers like that mainly go for dropping some blockchain mining software (monero is popular payload) and sometimes go for deploying botnet agents for things like DDoS ransoming and similar.

Low success rate, but low effort on attacker's side, who often buys a premade tool on a forum.

Ransomware targeting server data, primarily.