Some left to start their own companies, some went to Uber, and some haven't publicly stated yet. Everything I said is easy to verify via Google (there are articles written about it). The heavy hitters are Sebastian Thrun who left many years ago, so that's now really news; Chris Urmson, who was the face of the project, left about a year ago; Anthony Levandowski left to start his company (but really to join Uber since that was clearly the idea from the start) and took some people with him; and two of the lead software engineers started Nuro.ai