We can't blame it all on one thing. Obviously guns don't cause mass shootings but attitudes that enable mass shootings need guns to work. The example you gave of atomic bombs illustrates this. Obviously atomic bombs don't cause atomic bombings. There are thousands of atomic bombs and only two examples of them being used in war. But the attitude around them during the Cold War was "if the enemy is going to kill everyone on the planet, we'll be ready to do it first." This mass murder of the entire human population was the policy of the United States and the USSR and rationalized with what seemed to them as impeccable logic. There was an anxiety that the war to kill everyone must be won. But it would have been useless without the actual weapons.
The attitude the article explains is not so much a disregard for life, although I'm sure that part of it, but American society's ideology of success and how the pressures drive people into marginalization and alienation. We talk about these people as having mental problems but what do we do to prevent it? What do we do to get them help? I'm sure people seem quite satisfied when they can easily explain how these shootings happen after the fact. They can call them crazy. They can blame them for being "bad guys". They can call for harsh punishment. But people are still dead and it's going to happen again.
