The FAANG division that I was hired by (quite a while ago) was totally new, and had a very specific task involving software & hardware. Two headhunters worked full time to build the initial team of around 50-80 people in 'stealth mode' over a period of around 4 months. Only superstars who were capable of working in a team were hired. Most were approached by us out of the blue. Salaries were around 5 x industry norms plus stock (not just options). You can't find the people you want locally, so our relocation offers were rather expensive. We delivered the product to the global market in around 14-16 months. (We hired around another 500 staff a bit later - once we left 'stealth mode' we got a lot of media coverage and so received a huge number of unsolicited resumes. For a year or two I had to review around 1000 a month)

In more recent times I have heard of a London based quant software firm which does the same, and I believe DeepMind is similar.

I'm sure there are many firms who simply want the most experienced staff they can find to ensure the success of specific products or projects.