Prettymuch sheer will of the fandom since the 80s. The old-school ranger was very hard to make into an adequate archer (DEX was one of the few stats it didn't have a minimum requirement in), which was Robin's big thing (especially as he had been perceived in pop-culture from the 30's through the 80s), heck, in 1e, by the time it got followers -random, weird, supernatural followers for the most part - it also had spellcasting.
Yet, it was the woodsy fighter sub-class, so there was just this collective psychic force pressing on TSR like a million voices crying out, and not being silenced by anything but an "unofficial NPC Class" 'Archer' with an Archer-Ranger option in The Dragon.
Talk about zeitgeist.
And a noble-born knight back from the crusades, and a leader of a largish band of insurgents...