>such a large company would run into such a basic issue
Every large company is just a conglomeration of smaller departments. Each department had individual contributors. Some individual contributor in that department wrote the code and if nobody else is their department caught it, nobody else at the large company would have caught it since they have their own work to consider and don't have time to look at other people's stuff.
But, that's not how these things work. It would be nice if every department had unlimited QA resources, but most likely there have at most 1 QA person, and might be sharing that person with other departments. So if that person misses it then...
Every large company is just a conglomeration of smaller departments. Each department had individual contributors. Some individual contributor in that department wrote the code and if nobody else is their department caught it, nobody else at the large company would have caught it since they have their own work to consider and don't have time to look at other people's stuff.