Back when quarterbacks called the plays, substitute players were forced to sit on the bench by rule, and substituted players were few, teams commonly placed their helmets in neat rows along the sideline. I've never figured out why they did so. I am aware that Boston College placed their helmets on the ground in a “V for Victory” formation before the 1943 Orange Bowl. However, the Eagles did not soar as high as the Horned Frogs jumped, losing to TCU 37-21, so superstition is not an adequate explanation.
Shooting from the hip, I’d guess it’s related to the overall culture of pseudo-military football organization. The fact that it still permeates today says something about how big it was back then. Quarterbacks lead their troops onto the field. Linebackers are field generals. Linemen do battle in the trenches. Good passers have cannons. Etc. It’s a completely ridiculous circus today, but the way it came into the game through coaches and players who were veterans is neat. But I do hate hearing about how a QB that can’t be touched is “going to war with his teammates”. Give me a break.