Meh, past a certain base of technical understanding (enough to talk through solving a programming problem on the phone), it's all connections and soft skills. At Microsoft if you get an interview for an internship there's like a 50% chance you get the offer, but like 1% of the people who apply actually get the interview. And even though these companies have at-will employment, in reality it's INCREDIBLY difficult to get rid of people if they don't want to leave, and with big tech they often print enough money that it's either not worth the hassle of firing slight underperformers or it's not worth getting rid of proven engineers who have nothing to work on right now and having to find actually good new senior engineers to hire if and when the need for them arises. There's no industry that's really immune to nepotism/cronyism IMO.