I'm not GP, but that information is actually publicly available from the people involved, here's a basic summary if you're interested: Gabe Newell invited Mich

I'm not GP, but that information is actually publicly available from the people involved, here's a basic summary if you're interested: Gabe Newell invited Michael Abrash to work at Valve (they knew each other from back at Microsoft, and Abrash was even offered to be a co-founder of Valve originally but turned it down). Abrash was interested in wearable displays as a future platform. Valve missed mobile and even wants to reduce their dependence on Windows, so there's justification to research it and put together a team.