Other than Bryson, the swings aren't nearly as "violent" as you may think. First, I think the injuries are a little over-reported. We have better medicine today (meaning the overall state of the industry), and the players make so much money that they can afford to take time off to heal or have surgery. I would venture a guess that players used to just play through a lot things we hear about sidelining players today and got healed up from October through December every year. Now, the season is 12 months, so there's no real off season.
Secondly, the more modern golf swing has a big emphasis on correcting key stress points (mostly the back and neck). You never see the "reverse C" any more with legs and knees running wild ahead of the arms/hands (think Johnny Miller and a young Jack Nicklaus). Lots of emphasis now on rotating the spine on a constant angle by using the core rotation from just below the hips to the shoulders. Nearly all the modern players have benefited from this to some degree, with a few exceptions like Joaquin Neimann who are kind of throwbacks to previous generations.
In contrast, as a whole, these guys practice more than previous generations. So there is the possibility that there is more wear and tear due to that. Even with better technique and conditioning, the golf swing is a very un-natural movement for a human.
Yes, Koepka has had his share of his injuries, and that may just be a result of his particular swing. Koepka does a lot of "unconventional" things in his swing and he hits "against" parts of his body, particularly his hips and knees. There's a lot of active resistance in his swing, especially against his left leg and knee. Don't get me wrong...his swing is fantastic. It just may not be built to last.
These guys are creating outrageous swing speeds for a number of reasons: (1) better swing mechanics; (2) longer/lighter/better shafts; (3) better physical strength and conditioning that is tailored to specifically increase swing speed; (4) many of these guys are simply bigger/better athletes. It's a young man's game because distance rules right now, and young guys are always going to hit it farther than older guys. For better or worse, that's how the game has evolved.
My long two cents...
I think the bold part is key. The modern swing is built around a lot more resistance......generally. Which is not good for longevity.
Maybe I'm imagining things, but guys seem to be breaking down much more and much earlier than in the past.