There are tens of thousands of studies out there. This one is a meta-analysis, which are often more useful than others, but it remains one study.
If indeed the evidence shows that masks didn't help stop the spread, then the scientific community will embrace that evidence.
How do I know that? Because (1) they are scientists, and (2) no gigantic conspiracy exists to squash the data.
Every goddam thing with you simpletons is a conspiracy. Every. Goddam. Thing.