Why are modern men so lacking in courage?
The answer is; because they lack that which sustains courage - which is 'religion', which is some-thing deeply assumed/ lived-by that is transcendent to this mortal life.
Without this; the bottom-line is expediency; which is the opposite of courage.
Yet in addition, the nature of courage has changed - which is why even the few Christian and religious Westerners are lacking it.
In an inversion (one that complements and compensates-for the moral inversions of modernity) what used-to-be courage has now become expediency
In the past, courage was a social virtue. It was a type of conformity to the group. Its special characteristics were obedience and loyalty. Thus the courageous individual was not required to strike-out alone nor be independent; but rather to assimilate to the group ethic: the group defined the ethical.
Courage was standard recommended behaviour - and the problem was subordinating the individual preference to conform to the group preference. Courage was doing what the group recommended.
(Military courage is of this type; and so is the courage required of a saintly monk.)
In other words; in the past, virtue was defined by the group, and transgressed by the individual.
Now things are different and almost the opposite. Virtue is individual (or not at all) because society is corrupt.
To be obedient and loyal to any modern group (institution, corporation, church etc.) is expedient, and to lack courage: to be on-the-side-of evil.
Courage must therefore be individual, goes unrewarded (or is often punished) by society and social institutions; and the needful courage is cold rather than hot.
(Hot courage is short-term, unthinking and in the heat of the moment. But cold courage is considered, long-termist and must strive-against against the continual pressure of unrelenting opposed expediency.)
Modern courage is 'a big ask' of anyone; and only those with a supremely strong and inner reason for courage are capable of it. Extremely few modern people have any such inner reason; hence cowardice is not only the norm (which is not unusual) but is actually praised and regarded as virtuous by society.
Only a solid and powerful adherence to some-thing transcendent (something located outwith this mortal life and temporary earth) is able to sustain such individual cold courage.
So, courage is nowadays not something that can be recommended by worldly criteria; but only by and for those who fundamental perspective is 'not of this world'; for those who genuinely look for validation and reward primarily beyond this mortal life.
Note added: The fact that Modern Men are indeed lacking in courage ought to be obvious to the meanest intellect; however I became personally aware of this fact through many and sustained personal experiences in four main areas of contemporary life: Medicine, the National Health Service bureaucracy, Science (specifically medical science and biology), and Academia and Education more generally (since I was also engaged in English Literature and Philosophy; as well as having a professional interest in the history of education, education policy and scientometrics - i.e. the quantitative measurement of academic outputs).