Apple makes cutting edge hardware, at least two operating systems and lots of user applications. Google makes search, cloud, a decent office suite with the largest mail server in the world and of course cutting edge AI. It's easy to see why either of them needs twice as many people as Meta
Whatsapp powers entire economies, outside of North America. And then there's Instagram. If we're going by that reasoning, Meta's undersized.
Also Google has a whole YouTube inside of it