They interview people from everywhere. Literally everywhere. They basically have tapped the whole market worth of talent.

You might not get an interview at any given company in a particular year, but you should be able to get some interviews over a couple years if you have decent GPA or work experience. You probably won't be placed on a top-notch team, but you'll get in.

this may have been true at some point in the past, but it certainly isn't now. most of the engineers I work with have degrees from schools I had never heard of before meeting them. my team just hired a new grad that didn't even have any internships in school. it's not hard to get an interview at FAANGs these days. the difficult (or "luck-required") part is actually giving good solutions to four out of five algo problems, each in 45 minutes.