Artificial playing surfaces have a lot to do with it, despite technical improvements from the first Astroturf days.
So does the fact that today's athletes are bigger, stronger, and faster than they were a generation ago.
So does footwear. The incidece of ankle, lower leg, and foot injuries has gone up with the universal adoption of low-cut ultra lightweight shoes. Jon Arnett had Barry Sanders-like moves that unfortunartely weren't preserved amid the breakaway runs that make up highlight reels; and even when low-top shoes came in, he insisted on wearing his high-tops.
My boxing high-tops were extremely light, soft, and flexible - and permitted full uninhibited movement, up to a point. Beyond a certain degree of flexation they didn't bend and the foot stayed stabulized, for example if you fell sideways and caught an edge.
Bone structure also comes into play. The thicker boned athlete has more area for a tendon to knit into.
And then there's conditioning. Sometimes the bulked-up, chiseled guys whose muscles haven't been developed to allow full extension and contraction get hurt more often. Ligament and tendon tissue takes longer to strengthen and responds differently to certain stresses than muscle, and require a different strengthening regimen than three sets of ten, etc.
And some guys simply don't react to momentary stress the ways others do - they get hurt more easily because of how they respond to impact.
Recovery, following injury, is another matter.
