Populism Loneliness – so what is the link between the two?
Hannah Ardent was one of the first writers to make a link in her book The Origins of Totalitarianism. 

So Populism uses loneliness of a certain part of the population for its own ends. The lonelier people are, the less they belong. But if a marginalised part of the popualtion feel they don’t benefit from the prevailing system. So a section of society that doesn’t belong.
Populist politicians know and can capitalise on this. Create an ideology for the disenfanchised. This creates a new belonging. More votes. 

The move to cities, leaving rural communities behind. The fall of old Industry. The rise of Neo Liberalism .Seeing individuals as competitiors increases the sense of isolation and loneliness. Communities who are excluded and ignored are angry and yearning for a cause to belong to.
The lonely see the world as more unfriendly and threatening: so are more hostile to others.

Like the isolated mouse presented with a new outsider mouse. It attacks the new mouse. The disenfranchised want to attack and lash out. Against immigrants, the Liberal Elite, and anyone who else benefits from the economics of the time. The gap between rich and poor is a fertile ground for Populism.