Early free divers used goggles (and were in many places called "gogglers") but the goggles only avoided squeezes because they leaked fairly badly - allowing them to equalize on the way down.
Early masks also leaked equally badly and clearing a partially flooded mask was something you did frequently. That was at least the case when I started freediving with an inexpensive oval single sealing edge mask that was in most repects very similar to the masks of the 1940's and 50's. From there it is a small step to clearing a fully flooded mask.
The thing I think people tend to forget is that people who dove back then were by definition very comfortable in the water and almost always had freediving experience prior to taking up scuba. So a skill like removing, replacing and clearing a mask was a no brainer.
What is interesting is to watch old scuba films and watch divers clearing a mask by tilting the head sideways and holding the "top" side of the mask to the face. Since I usually see the diver roll to the left to do this, I suspect this was possibly related to rolling to the left to clear the hoses on a double hose reg lacking mushroom valves, and/or to assist in clearing the exhaust hose on a double hose reg with mushroom valves, but I am not certain of this.