That's usually the way it works.

Google also has a bunch of ex-Microsofties (dream company of the 1980s) and ex-Amazonites (dream company of the 90s).

It pays to get into a dream company as soon as possible, and do cool things there, because other companies will see those cool things and give you your pick of jobs.

luck probably didn't play that much of a role in Google hiring them, given that they already established major cred at Bell labs.