I'm confused

Seriously - "It said a trojan was found on the personal machine of kernel developer H Peter Anvin and later on the kernel.org servers known as Hera and Odin1"

So a Trojan infection, was this a Linux machine or a windows pc?

If Linux then the Trojan would have had to trick a (presumably) tech savvy user into installing and giving appropriate privileges to it. If windows then the same would apply (and presumably said tech savvy user would surely have had up to date AV / malware programs running)

The real question I suppose is how it happened and not the why

Serious, not having a go or my OS / your OS posturing, just how he got the Trojan

(may already be in the article, going to have a re-read now)