Maybe it's more of smokeless powder that did not obscure target to the nearby shooter, and faster firing rifle that made the case for mass armies - line infantr

Maybe it's more of smokeless powder that did not obscure target to the nearby shooter, and faster firing rifle that made the case for mass armies - line infantry that took years to train so there can't be too many of them coz economy won't be able to feed so many people who don't plough the land, for so long - made way for huge conscript armies you can raise in months. Suddenly everyone had so many more men able to fight, and when you have a hammer, everything looks like a nail.