Note that our feelings are influenced greatly by social comparisons. For example, those whose immediate neighbors are all poorer than they feel much happier than those who are richer but the poorest in their immediate neighborhood. As Buddha said, expectations tend to rule feelings.
Modern society, both for dating and friendships, sets up false expectations ("The Illusion of Choice"), that often leave us without partners. Some combination of finding a crowd you like better, and lowering your expectations has to suffice: or nothing will.
Meanwhile men went to work where people have no choice but to communicate with you. You don't have to put effort into relationship, you are guaranteed not to be really lonely. In fact, too much relationship can be detrimental as you all compete for position and salary etc. Being a bit of jerk can pay of and you don't have to care whether people like you - if they don't it is up to them to deal with it. Plus there was influence of past war on expectations on males (be like veterans are).
That leads to two different kind of socializations for boys and girls - where boy socialization leads to loneliness in long term, when you are too old to pick up new habits.
As I understand it, „loneliness” in the article is understood as the feeling of loneliness, not a measure of how sociable you are. You can be lonely while continually being around people which you have relationships with which look warm on the surface, but don’t give you much of a satisfaction. I think it is the case with a lot of people suffering from depression.