the song, and the jokes were the way of distracting themselves from the futility of war.

You can analyse all you want and massage your own egos by discrediting this hypothosis or that. But it was written and became widespread because it gave an outlet that in other circumstances would have been insubordination.

And it is well documented that it irritated the higher echelons to the point of being more than frowned upon, and even banned.

And it chimes today in the myriad versions, plus modernising parodies.
That is powerful Folk!