Correlation is evidence. You might be asking for a proof, but proving causation for historical events is nearly impossible. Overwhelming amount of correlation

Correlation is evidence. You might be asking for a proof, but proving causation for historical events is nearly impossible. Overwhelming amount of correlation is as good as it gets. For example if you can see the same trends in other regions where inflection point strongly correlates with social networks entering the market (i.e. being launched/unbanned/localized).