Pandemics causing death are linked with increases in support for radical political movements, all the way back to the 1918 flu pandemic and the birth of 20th century fascism
Evidence linking past experiences of worsening health with support for radical political views has generated concerns about the consequences of the COVID-19 pandemic. The influenza pandemic that began in 1918 had a devastating health impact: 4.1 million ...
"When and if fascism comes to America it will not be labeled 'made in Germany'; it will not be marked with a swastika; it will not even be called fascism; it will be called, of course, 'Americanism' " - Halford E. Luccock
Evidence linking past experiences of worsening health with support for radical political views has generated concerns about the consequences of the COVID-19 pandemic. The influenza pandemic that began in 1918 had a devastating health impact: 4.1 million Italians contracted influenza and about 500 000 died. We tested the hypothesis that deaths from the 1918 influenza pandemic contributed to the rise of Fascism in Italy. To provide a “thicker” interpretation of these patterns, we applied historical text mining to the newspaper Il Popolo d’Italia (Mussolini’s newspaper). Our observations were consistent with evidence from other contexts that worsening mortality rates can fuel radical politics. Unequal impacts of pandemics may contribute to political polarization.
Something not considered in this paper, Post Viral Syndromes, may also be a factor. Though some acknowledgement of post viral syndromes dates to at least the 1950's, it's only with the COVID19 pandemic that modern medicine has really begun to take a look at this with some seriousness. These PVS's can affect many organs in the body, specifically the nervous system, and including cognition.
It looks like me like they just mean that their source for region by region how many people had died, and what the support was for fascism in the elections, was pulling the data from this one specific newspaper at the time.