I think all global scale companies have two things they do really well.
ALL of them are really good at scaling. It's really hard to take something that works, and make it work billions of times a day.
ALL of them also have one thing they're good at, and are able to capitalize on that to get enough other things going that you use their main thing without realizing it.
Google is good at advertising. Everything they have feeds in some way into this model.
Facebook is also good at advertising, but it's a completely different model.
- Note that Facebook only loses in advertising scale and scope to Google. Those two account for 90% of advertising in the (outside of China) world.
Apple is really good at making devices that work together and keep you using just those devices. They're a walled garden company, and they're good at it.
Amazon is really good at store fronts. Everything they have advertises something else of theirs, and nearly all of those advertise things they're reselling.
Microsoft is really good at platforms to build things on. Windows? Okay OS, amazing platform to put other things on. Azure? Amazing cloud platform. Xbox? Great gaming platform, etc. They aren't good at consumer facing things, but they make great platforms.