A starting note: I don't disagree with you (about systemic issues), but I want to explain what I understand as the perspective you are responding to.
A "scapegoat" is someone who is incorrectly blamed for someone else's errors or sins. The perspective you're responding to is this: They built the system, they run the system, they have continuously warned "This system is dangerous!", and yet persisted. That is not being incorrectly blamed, not being a scapegoat, and instead is a collaborator.
So I think you mean to ask: "Why do people focus so much on finding someone to blame?" It's not merely semantic, because the answer to that is more straightforward: Consistent accountability is a major factor in deterring bad behavior. It is not the only factor, but it is a major one.
That is my Steel Man understanding of the people searching for individual blame.
Sometimes in "normalization of deviance" situations, there isn't anyone specifically to blame. I wouldn't make an assumption that you can find anyone particularly blameworthy without doing an investigation first.
The rate at which these "labs" are creating these incidents is simply staggering.
Imagine we made nuclear weapons a private industry, had CEOs bragging how they have enough warheads to blow the Earth to smithereens, and then they "accidentally" nuked three cities over a short period of time each, saying they lost control, or rather couldn't contain their semi-autonomous weapon. All somehow managing to turn the PR around from their abject incompetence and towards SciFi visions of mankind hunted by self-replicating bombs.