They just employ the people who do? And, until recently, the paid language evangelists?

Google employs a few people who have a commit bit, but they are handed out via consensus among the whole team, not by a single company or its employees.

Right, and at one point the whole team were all or mostly Mozilla employees (which, financially, is a client company of Google). So the core team is a group of Mozilla alumni and their friends. Unlike, say, C++ which is under diverse committees across multiple countries.