I didn't say everyone wore masks - but some did believe it would slow spread, and so wore them and tried to get others to do so. Things that are seen in historical photos generally are not "completely and totally" made up. It probably had no effect; they would have been using cloth masks with large holes or gaps, and the flu virus is small. But people often do things to attempt to protect against illness that have no effect.

-Translucent Jejune Octopus