People may be more willing to hop, but they'll be able find new hires. Check out the number of applicants to any "Meta" job opening on LinkedIn.
Facebook, Instagram, and WhatsApp are built. They have their management systems and structures in place. It would be wrong to think that everyone at Facebook needs to be a genius for the company to succeed, and putting a genius into many of the roles that are needed to keep the company operating won't work out well for either the genius or the company.