If you go back even a couple of decades, people had only two or three trusted sources of information (radio, TV, newspapers) and if you go back a century that becomes only one.
Actually one was better than three. Newspaper brought, since their inception in XVIII century, a wealth of contradicting, contrasting information and people had to face a plurality of sources, and take a position.
When "public opinion" was formed through newspapers, free thinking flourished. We own to the newspaper age the "enlightment" age, the modern liberal democracy, and a great lot of independence movements all over Europe (among those, the Italian struggle for independence, Italy celebrates this year its 150th anniversary from the "official" unification date).
Radio had an opposite effect. Radio entered into every household, included the ignorant masses, which were the vast majority of population, and gave a "truth", a "trusted source of information", without any contradictory. It just fell from above. It was like the word of God. It was for an entire planet like the Gospel. Radio favoured the birth of dictatorships all over Europe (especially Fascist ones, and Nazism in particular, which were in a sense greatly favoured by the radio). In communist countries, the radio certainly favoured the "personality cult". One Stalin, or one Mao, could be depicted as the omnipotent saviour of the country, the Godsend against the (many) external and internal enemies (saboteurs, anarchists, capitalists, Jews, priests, speculators, bankers and various other forms of traitors and parasites, according to taste).
Radio allowed any government (whether present culture defines it as fascist or not) to enter any household without contradictory, to distribute guilts, to give excuses, to create myths, to cement that particular blind form of "patriotism" which make every dissent a menace to the national health and wealth.
Countries which think are democratic (such as the US) followed the same pattern. Just imagine the enormous power the weekly President's radio speach had over the general public, or the daily government-controlled radio news had on ignorant masses. Television did not certainly improve the situation by itself. Only, in recent years TV and radio space become more "pluralist" and so somehow recreated the situation of pre-radio years.
If we analyse the political evolution of every country in the radio days we see an enormous raise of fascism in all its forms. Not just in countries like Hungary, Yugoslavia, Greece, Spain (during "carlism" well before the Franco golpe) etc. where suddenly fascist regimes managed to gain, and especially preserve, power, but also in so-called democratic countries, where fascist attitudes become normal and widely accepted. Just to mention the US: thousands of blacks lynched without any form of state intervention, massive control of the state over the media, "Palmer raids" against Italian and anarchist before the war, concentration of US citizens of Japanese descent during the war, ridiculous Nuernberg process after the war, MacCarthysm after the war, are all signs of a "fascistised" society, a society where the radio, or government controlled TV, is the prevalent source of information.