It really wasn't false at the time; there's a bunch of uncertainty around it for this virus. For quite a long time, people really did believe SARS-CoV-2 could transmit through surfaces easily. We now know that to be incorrect.
People may or may not have believed a lot of things, but if you are asserting that they didn't know that respiratory viruses primarily spread via the respiratory system you must be joking?
If you can show me even a single document dated from before Fall-2019 that expresses a concern that untrained users of n95 masks may INCREASE their chances of infection by coronaviruses, cold viruses, flu virus (basically anything other than Ebola or other hemorrhagic fevers) somehow, then I will happily agree that this was an area of debate and perhaps competent (but incorrect) advice to avoid mask usage.
However, if no such evidence exists, you should agree with me that the evidence points to incompetent and/or intentionally misleading guidance.
