We don’t know. But as you read from the article, Meta’s own employees were concerned about it (and many other things). For Zuck it was not a priority, as he said himself.

We can speculate. I think they just did not give a fuck. Usually limiting grooming and abuse of minors requires limiting the access of those minors to various activities on the platform, which means those kids go somewhere else. Meta specifically wanted to promote it’s use among children below 13 to stimulate growth, that often resulting in the platform becoming dangerous for minors was not seen as their problem.

If your company is driven by growth über alles à la venture capitalism, it will mean the growth goes before everything else. Including child safety.