[nostrademons]

I thought that basically David Cheriton made the introduction to Andy, invited the founders and Andy over to his house, and then Andy decided "Cool, lemme write you a check", and then David was like "While I'm here, lemme write you one too." In contemporary fundraising parlance, Andy led the round and David co-invested. The circumstances are covered in a bit more detail in In The Plex, although IIRC that didn't say that David invested, only that the meeting was at his house.

My guess is that David Cheriton, famous for keeping a low profile, didn't want it to be known that he was a billionaire through Google, and they honored that wish. But sometime fairly recently somebody else outed him (I recall reading an article a couple years ago that mentioned him as Silicon Valley's wealthiest unknown billionaire), and at that point the cat's outta the bag.