It's worth stating that Google has been hiring like crazy for years. In their Q3 earnings[0], their year-over-year number of employees increased by 36,751.
Back when I was in school Google was the company that had an aura where it's reserved for geniuses and next to impossible to get into.
That was a number of years ago, I can't help but notice this perception changed among the people I know. I don't think it was entirely because I graduated and start having experience (disclaimer: did not work for Google).
I'm sure there were tons of great engineers at Google, and they probably were incredibly picky with college grads. But I also saw them hire people I had worked with that were experienced but not amazing performers. There are people who have good resumes in that they went to a good school and somewhere along the line worked at a well regarded company. The funny thing is that people like that are typically well regarded their entire career even if they just bounce around. The pedigree doesn't go away. It's hard to evaluate people.
This perception changed 5-7 years ago. I actually can't think of a single software company that induces the same level of awe in university students anymore. Places like Jane Street do but they aren't really Silicon Valley tech companies.
Deepmind is high status as well. However with both these companies - they are looking for experienced researchers usually rather than new grads. Google was famous for hiring bright eyed young geniuses and building their careers.
They used to be quite a niche trading company, known in the functional language community for their use of OCaml. But they grew to one of the highest paying company in the world.
Jane Street did outreaches at MIT (dunno which other schools), wrote blog-like things, used an exotic language, paid a lot of money (word gets around), etc.
It's probably just size. People might believe a company of 20,000 is filled with geniuses, but it's hard to imagine a company of 200,000 filled the same way
[0] https://www.sec.gov/Archives/edgar/data/1652044/000165204422...