I believe one of the major problems for men, rather than women, is that men are unable to build genuine supporting relationships in the way that women do.
I am generalising, but women will confide in friends, trust them with confidences, turn to them when they need comfort support and advice over trivial things, so they are used to it, and easily do the same when things turn serious.
Men's relationships are generally more superficial, based on conversations about abstracts like sport or jokes, there is no real bonding there, so there is no actual real support when it comes to be needed.
A man won;t confide in his friends because his friends wouldn;t know what to do or say.
That I beleive is a large part of the issue facing lonely men.