First of all you can't think of soldiers of the 21st Century the same way you think of the 19 year old kids with M-16s stomping around Afghanistan. They're more like Knights, closer to SEALs than Knights, but still, the concept of an individual professional warrior commanding a host of infantry isn't new, its just making a comeback. It started out small at first, mostly in Iraq and Afghanistan when Officers began begin educated almost as anthropologists to better know and treat with local forces. It will grow as the US begins to shift to a model of a few hundred soldiers training and functionally commanding a few thousand local forces. As drones become more autonomous they'll be lumped into this system of educated proffessional soldiers and uneducated infantry. As the Little Cold War continues with Russia, and the Eurasian Cold War with Turkey and Japan comes into the fold, another four decades of frozen conflicts will limit the movements of full scale invasions, and further force the US to expand its reach with smaller well trained professional soldiers who even in lower ranks must command huge numbers of infantry and drones. Additionally, cost cutting measures and a war weary public are further driving the government to take fewer risks with American lives right now. If ISIS existed 10 years ago, Bush would have sent half a million men to Iraq and gone to War in Syria.
Its a comedy of coincidences feeding into long lasting trends such as declining birth-rates, economic interdependence, precision warfare, and unmanned systems.