The topic is multifacedted and I cant pretend to understand it fully, but to speak of some aspects as I understand them
There is a large gap between societal and cultural expectations of men, and the financial and realities for everone at the moment.
One part of societal expectations of men is that they expected to be independent, capable of getting and holding a job that pays well enough to buy a car, own a house, etc. The current reality is that many men are in debt after a university degree, have a hard time finding a job because 99% of applications get rejected outright, and get paid significantly less accounting for inflation and costs compared to their predecessors. It is impossible for the average person to afford a house on the typical wages these days without already having a significant other or by pooling resources. This has led to a large number of people who live at home and have less money to spend on things like going out.
I say this as someone who is fairly well off given my job and field, I get paid ~2x what some of my friends do and I could not afford a house within a 2hr drive of my workplace. I live at home with my parents and it fucking sucks.
Another aspect of bad cultural expectations is that men are expected to be cold unfeeling lone wolf types, and the idea that any sort of male bonding is "gay" which has caused people to spend less time doing things with friends. Men end up with smaller social circles and with less friends. With increasing costs and long working hours, they end up with little time to actually hang out together.
An additional aspect of the failure of cultural expectations to adjust the need to place blame. Blame has fallen on the individual man for being, among other things, lazy good for nothings, who are weak, ugly, etc.
If we look at the US, they have been abandoned by the left, both by the democrats (e.g. economy is fine, must be your fault), by the feminists (told to be vulnerable but called weak for being vulnerable, shunned at every instance because "sounds like a you problem" and "figure it out yourself") and by their own parents who had an easier time.
This is part of why the manosphere became so popular. Men have been told for so long that they were the problem, many of them still just boys, whereas right wing pundits like jordan peterson, andrew tate, joe rogan, etc gave them targets to redirect blame. An excuse for "actually, its not my fault I cant find a date, its the woman's fault," etc. Note that this is not my personal belief. It also gives them a sense of community and people talk to that actually listen and make them feel heard and justified in their struggles.
The blame game has caused us to ignore several important systematic factors. The rise of individualism, stagnant wages relative to inflation and costs, and growing wealth inequality, as well as the erosion of community and mens safety nets are all major factors which have decreased mens mental health and increased male loneliness.