What was the thinking of going with Forgotten Realms over say a Greyhawk?

@mikemearls question, what was the thinking of going with forgotten realms over say a greyhawk?

— Keith Martin (@kam2112) November 10, 2016

Surveys each week, kept open for a month, one per article. #WOTCstaff https://t.co/hFpcgJyjDl

— (((Mike Mearls))) (@mikemearls) November 10, 2016