it's timing as well, back then how many physiques like Arnie, Stallone etc were in the public eye? not many at all and the movies were something new and unseen too.
now most movie concepts have been milked a generation ago, not many cult classics in the action genre of film today because they've all been done and re-done decades ago and his acting ability means there's no chance he'll be involved in a cult classic-type movie in a different genre, one which relies on his acting rather than his physique and persona.
That's true as well. Back in those days, muscular and ripped physiques were rare and most of the other major stars in Hollywood (Ford, Gibson, Keaton, Willis..etc) had dad bods.
Now, all the top Hollywood stars have impressive and conditioned builds. Why get Dwyane to play the role of the action hero when you can just get an established actor...who, after a 4 month cycle, will look every bit the action star.