The bottom quartile at some of these companies could still easily be in the top decile at many other companies. Unfortunately every company thinks they need, and are deserving of "Top Talent".
I think you’re overestimating the hiring ability of big companies, and underestimating the people at small companies.
I think working at a bigger company is a somewhat different skillset involving a lot more navigating bureaucracy, meeting certification standards, documenting and presenting, etc.
Smaller companies focus a lot more on "get stuff done, figure out the details later"