He was brought in not only for his expertise but in hopes that he could reform a sclerotic design process that's stuck in the 90s. AMD, Apple and Tesla (places Keller was before Intel) use a lot more design automation and thus are able to get more done/engineer. Intel has a patchwork of tools that are generally internally developed (and thus no one outside of Intel has expertise with those tools and expertise with those tools is not transferrable outside of Intel either) and different design groups have their preferred tools. From what I gather Keller was trying to bring in more industry EDA tools and standardize the design process between groups as well. From what I hear from people who were there he ran into all sorts of push back. So I gather he's decided to cut his losses and leave Intel to languish.