Hello,
Of course, it could :
https://blog.malwarebytes.com/cybercrime/2016/03/first-mac-ransomware-spotted/
https://blog.malwarebytes.com/threat-analysis/2017/02/mac-ransomware-on-piracy-sites/
https://www.welivesecurity.com/2017/02/22/new-crypto-ransomware-hits-macos/
Cheers,