One is a former game developer (with only a high school degree) who happened to have an interest in ML and studied up in his free time. A few were in a startup, bachelors in Computer Science from non-Stanford universities, that was doing AI work and was acquired. Another is a developer of a prominent open source package, originally utterly unrelated to AI, but he started working on learning related applications with his software and landed at Google as a result. Another is a friend with a PhD but in a totally different area (Computer Graphics) who was hired into Google where she landed on a ML team.