I think it is a couple things.
Vs. 30 or so years ago I would say generally yes, but to some extent it's more about who is bigger and faster in my opinion. Thirty years ago there were guys that were as big and fast as the current players. However, I think those guys were pretty much exclusively the genetic freaks. Their ligaments and tendons were PROBABLY more likely to be equipped to handle the force their muscles could generate. Training has allowed a lot of guys that have good natural ability, but aren't natural-born freaks to do some super explosive things. Now, this is not really something that can be proven, but is more intuitive, but it seems like those types of guys connective tissues are not naturally equipped to do these things.
Second, I think there is still and has been a lot of the old ways of training and doing squats and quad/glute exercises where guys were (and are) taught to squat but not to get their knees out in front of their toes. So they are squatting huge amounts of weight, so getting ridiculous quad and glute strength while keeping their knees from getting out in front of their toes. But in basketball and football in particular, most of the high explosive take-off and landing is happening with the knees way out in front of the athletes' toes. So they are getting loads of power, but not training from the most common knee position where high force occurs.
Now the 'knees over toes' exercises are a lot more common, but it's still way behind. This guy is typically credited with popularizing it. I'm sure there may be some holes, but from the little I have read and listened to him, it all makes a ton of sense, and taps into some approaches other cultures have taken in preserving mobility into old age:
Ben Patrick has a controversial plan to help you beat chronic pain—and transform your athleticism in the process.
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