When I was growing up, running backs were sort of the face of football. LaDainian Tomlinson was running for a 1000 yards every year and “The Bus” was somehow a RB at like 260 lbs. The NFL, and even college football to some extent, was old school. The RB carried the offense.
All that has changed. Running backs are hardly ever drafted highly anymore, as teams recognize there isn’t much difference between a 2nd round RB and an undrafted free agent. So many of the best athletes end up playing RB that there are a surplus of guys at the position.