In a recent interview, Dr. Anthony Fauci (Chief Medical Advisor to the President of the U.S.) was asked why he advised the public against wearing masks in early 2020. One of Dr. Fauci's arguments was
"There was no evidence at the time that masks outside the setting of the hospital worked; there were no data to show that".
Is this argument valid? Sound? Reasonable? To me, it seems extremely flawed. If there is indeed data showing that masks work inside hospitals, it's trivial to extrapolate that they will most likely work outside of hospitals as well. Is there a fallacy going on here?