It's not just the feel, it's not just the chops. It's the blending of both.
Bebop, Hard Bop's immediate predecessor, boasted many instrumental masters, but in their effort to realize more of Swing's harmonic and melodic potential, sacrificed the "down home" quality with which jazz had originally been associated. (The notable exception, of course, is Charlie Parker, whose nearly every solo was blues-drenched.)
The creators of Hard Bop brought that feeling back, adapting chord progressions from the church, and melodies from the rhythm-and-blues groups that sprung up in the 'fifties, and so restored jazz to its former place as a popular music, at least in black neighborhoods. As they did this, they expanded the vocabulary of all jazz instrumentalists to the same as degree as, if not to a greater degree than, their bebopping forebears.