For the men going into that carnage, there was a sense of patriotic fervor prevailing over all anyway. Added to that was the notion that the Almighty Himself was on the side of Britain - this demi-paradise, this other Eden - and what further evidence was needed of that than the fact that the sun never set on the British Empire?
Mons was a slap to morale, that was true. But the Almighty had so marked Britain for greatness, that even its dead returned to make good any deficiencies. Nothing could possibly go wrong.
For the wives, mothers, sisters, daughters and sweethearts left at home, it was a comforting thought to imagine that something supernatural would keep their men safe. If not God, then ghosts.
For the owners and editors of newspapers, it was a story which sold papers. Hence it kept on being told, with embellishments and in differing versions. This is why the legend as exists now isn't quite the same as that printed as The Bowmen.
For the clergy, there was much to recommend in this tale. Though they didn't know it, they were presiding over the last generation of British with an almost universal Christian faith. The First World War would do much to shake those beliefs, hurtling Britain towards widespread secularism.
Even so, vicars and priests across the country were increasingly having to deal with the loss of substantial parts of their congregations. Every person killed in battle required a memorial service. Each casualty left behind those in mourning.
This was the age of the 'Pal's Brigades' - friends, brothers, groups, whole communities of men - who would enlist together, serve alongside each other, and frequently all be killed en masse. Clerics were facing situations when every single member of their flock had lost somebody, and had to make sense of it.
Any wonder then that the Angels of Mons featured so heavily in sermons across Britain. Here was 'proof' of God's hand in the war. Here was the evidence that they weren't forgotten. For those losing their religion, this was also the counter-argument that God existed.
It was in Britain's churches that the longbow-men and cavalry ghosts became angels, and that was why.
For the government, the Angels of Mons was a useful propaganda tool. No smoking gun has yet been shown, proving that the War Department was behind the scores of 'eye witness accounts' that began to creep out, as the war progressed. But it does seem likely.
This theory is explored in depth by David Clarke in The Angel of Mons.
As for Arthur Machen, he constantly, loudly and publicly denied that he'd ever received any 'secret intelligence' from government, nor had he interviewed the exhausted survivors from the Battle of Mons to receive the story.
It was his own, influenced by nothing more than the history of Agincourt coupled with elements from Welsh mythology - particularly King Arthur hearing the clarion call to come and save them all, or Y Ddraig Goch rising from its cave to fight back the Germanic White Dragon - and placed in the modern day. A ghost story interwoven with Cymric Mysticism, just like 90% of everything else that he wrote.
But no-one cared to hear that. In the terrible aftermath of Mons, it was a story that soothed the national psyche and that was all that mattered.