It's even older: The myth of individual excellence is at least as old as the phenomenon of a distinct class of a warrior aristocracy. All throughout history, you'll see the elite (as most historians and poets were, because a peasant working for subsistence doesn't have the time to write deep musings about that time he got conscripted for war and stood in a line with all the other common peasants) writing of this or that great general or warrior, despite most of just about everything being done by groups.

You might know about the great heroes of the Iliad, excelling in battle by taking down a key figure of the opposing side, but most people probably don't spend a lot of time thinking about the mass of "common" infantry on either side, let alone about the servants carrying the hoplites' stuff.

You might find a lot of medieval works focused on the glory and honor of a knight, but the (comparatively) poor spear-and-shield conscripts receive attention mostly in official documents detailing the way their army was to be raised (see the section "Ninth-Century Rohirrim" here).

Even when thinking about heavy cavalry charges, for the longest time I never gave much thought to the value of coordinated cohesion between them. The knights' charge is still a group effort, where an isolated warrior - great hero or not - would be doomed. And while we may be aware that knights had a squire, the rest of the retinue wouldn't be clear to everyone:

Clifford Rogers notes one (fictional and lavish, but not outrageous) war party “suitable for a baron or banneret” included a chaplain, three heralds, four trumpeters, two drummers, four pages, two varlets (that is, servants for the pages), two cooks, a forager, a farrier, an armorer, twelve more serving men (with horses, presumably both as combatants and as servants), and a majordomo to manage them all – in addition to the one lord, three knights and nine esquires (C. Rogers, Soldiers’ Lives through History: the Middle Ages (2007), 28-9).

(Citation copied from this entry of the same blog as before)

Ever since there has been an elite with the leisure to write and document, served by a lower class who didn't, there has been a tendency to emphasise these elites' individual value and omit the group effort of all the invisible people contributing to that value.

I don't know if that is the cultural inspiration for the modern trend of focusing on single individuals or simply a symptom of a similar cause, but there is a certain resemblance that I suspect isn't pure coincidence.