The way I interpreted that sentence is not that fascism was established and flourishing back in 2016 when this was written, but rather that the fascist ideals and concepts were being openly pushed without (enough) sanction by the mainstream.

The reason why I interpret it that way is simple: when fascists are actually in power, there's no such thing as "mainstream" anymore. Authoritarian rule means that there's only one correct way of thinking and behaving, and everything else is a crime or heresy or "evil", depending on the specific flavor of authoritarianism. "Mainstream", on the other hand, implies that there are other views and that they can be discussed.