This is where critical analysis of the greats blunts progress. No one really has the ability to criticize either of these icons until they themselves become legends.
The rate of injury was probably pretty low. They use light weight (for them lol) and high reps. Arnold did like 16 in that last set. They were training to induce maximum pump.
Steroids or not these men are legends. A lot of the dudes on here have run anywhere from 1-6 cycles of PH's, which are steroids and look nothing close to that. Don't let **** become counterproductive. Building muscle is EASY. Lift for progression, eat, recover.
Point being, for them it clearly worked. I wouldn't waste time worrying about what the greats did and focus on what I can do to get there.
All in my opinion