The impression I get is that Intel has a lot of money to throw around, and they're trying to make big inroads into the GPU space over the coming years, so they're willing to pay a lot for people with existing experience in the field. So that shouldn't really be indicative of the executives not having confidence in the company they work for, just that someone else is offering them more.
And for all we know, AMD might not be paying some of these guys more because they might not feel they are worth paying more. Their graphics architecture may be catching up with Nvidia's, but there's no telling whether these guys are responsible for that, or if they were more responsible for AMD falling a bit behind to begin with. AMD has released some competitive products in recent years, but they also sometimes do things that don't always make that much sense. So, it's possible that AMD might be happy to move others into these positions, or at least they might not consider it a substantial loss.