Money is not all but FAANG have benefits and work that are comparable or better than most startups/companies. The overall package is just better... It's obvious to the market at large. Only niche audiences are willingly going to choose startups/companies with certain perks. (fully remote work, for instance - it is a niche thing regardless of what people here say)
Sometimes it's also about expectations, role, office location, other bonuses, etc. When in 2019 you don't let people do home office... Byebye...