Unless you have worked with Oracle or other big enterprises, you may not realize the scale of how these companies operate and the breadth of what they actually do. Just by looking at their product page[0] you can see they offer software, hardware, cloud, consulting, support, and even financing solutions. In addition to the technology and product people (of which there are many), you also need HR, sales, marketing, accounting, support, etc for the entire global organization.
Sure, 100,000 people is a lot, but Oracle also does a lot.