To start with not all the men who attended William in the recovery of Great Britain to civilization were Normans! Secondly, not all the Normans spoke Norman-French. Thirdly, Norman-French was not necessarily a widespoken language, even in Normandy, if it was, in fact, spoken at all.
What you may or may not be personally aware of has no impact whatsoever on the reality of any given situation.
Since it's not my purpose to teach you about the Romantic Languages, I am going to leave you guessing about Gallo. Was it like French, or was it like Irish? The answer is on the Internet!