Intel is the Big Dog on the block, has been for a while. Even had claims of 90% of the internet being run by Intel processors at one point not so long ago. Of course it's the target for such specific hacks trying to find back doors. And everyone has them, even Apple did. They are there. But Ryzen is still pretty new and is not yet fully established in business applications, won't be for a while, until ppl upgrade. That leaves Intel. Most ppl running amd are still using FX processors and haven't updated yet, and really, it's a pretty sad waste of time trying to hack an FX user. It's the same as Microsoft. Most ppl run a version of Windows, so guess who gets hacked. You can hack Linux just as easy, but what's the point, not enough users to make any real splash in the headlines.
Amd only looks better because either hackers aren't bothering, or those that are just haven't found the security lapses yet.