If your ambition is to be the best in the world, to push and explore the limits of the human body, then those amounts of anabolics are in fact needed.
And BTW, for me personally bodybuilding is just a hobby, I also have other goals and areas I want to grow and excel in. But that doesn't mean that for other people bodybuilding can't be their life and passion, nothing wrong with that.
It's easy to say in hindsight that Dallas should not have taken all the stuff and he would still live. What's important is what the chances of this occurring were ex ante. Race car drivers in the formula 1 face a risk of crashing and dying, but it's only a small chance, and so they decide that it's worth it for their passion. The same is true for bodybuilding.
It's true that the use of drugs increases the chance of dying young, but looking at the proportion of pro bodybuilders that had such an extreme health incident, it's actually not that large. Yes, by going all in on the drugs Dallas increased his chance of dying before 30 from say 1% to 5%. I'm sure he was aware of that risk and deemed it worth it, just like the guys in other risky sports like the formula do.