Without having seen the video:
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It half-assed defascization, as the DC [conservative] wanted to keep Fascists around in case communists got strong enough to win the elections
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The influence of fascistic networks like Gladio or Propaganda 2 allowed the far-right to be well connected among bourgeois, Mafia, church, etc.
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The Berlusconi government allied with the MSI [neofascist] successor party, and led a culture war blaming a huge chunk of problems in the country on communists. The PCI's successor parties were unwilling to defend communism as they had become social democrats open to former DC members.
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Huge influence of fake news, conspiracy theories and Facebook. The M5S was basically founded as an anti-vaxx, conspiracy theorist [interestingly, pro-degrowth], and Anti-establishment party, without having any real political program. After a lot of splits and having ruled together with the fash for a time, it settled on social democracy.
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The PD, successor of the PCI, swept back to power in 2013 and won big in 2014. Matteo Renzi's [former DC Youth member] government did Neoliberalism and a lot of people utterly hated him (so do I) for destroying Healthcare, education, etc. So the party's support crashed and went to the fash.
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The refugee wave of 2015+ fueled racism and great replacement theories.
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The WW2 generation is dying out, but pro-Mussolini nostalgia ("he made the trains run on time") hasn't
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