How would that be easy? If I put a random file on your computer X years ago while trying to cover my tracks, how would you tell when and how I did it?

Well this might be answered by asking who got it, what is their business, etc.

In general good malwares either try to make money or have some kind of geopolitical goal (industrial spying etc).

Information is power, but generally, a good hacker would know how to obfuscate the reasons why he is putting malware.

Attribution of malware can be difficult and the lack of details like who was targeted and missing plugins don't leave enough information to guess who might have been interested in developing this.

It's not actually shipping with Linux - someone installed a virus. That's really it.