Fascism has deeper historical roots, but the earliest acts and events that can be tied to its widespread rise early in the 20th century date to the early 1920s.
Racial supremacy, exclusionary nationalism, and fascism, started up or grew from earlier roots in the US, UK, France, Mexico, Spain, Italy, Germany, and many other places. In 1922 it would have been impossible to predict which nation or nations would give rise to a charismatic dictator with one or another final solution. (Probably Germany, yes, but Germany and what two or three other nations?)
The rise of facism consisted of acts of containment, harassment, and sanctioned theft by governments, as well as violent attacks against target groups and displays of martial power by both private mobs and governments. It involved individuals popping in and out of popularity, as populists, occasionally winning elections. It involved elected officials carrying out regular streams of illegal acts, and a great deal of corruption in the ranks of their supporters.
In other words, it looked like today.
The rise of facism took 17 years before the first Jews were put in German run ghettos (in Poland). But about half way to that point, facism had become unstoppable.
That is why the famous quote is famous. Learn and remember it.
That is why people today are making a legitimate comparison between things happening now, like putting assylum seeking toddlers in dog kennels, or neo Nazis marches, and then.
So, let us repeat:
First they came for the Socialists, and I did not speak out—
Because I was not a Socialist.
Then they came for the Trade Unionists, and I did not speak out—
Because I was not a Trade Unionist.
Then they came for the Jews, and I did not speak out—
Because I was not a Jew.
Then they came for me—and there was no one left to speak for me.