The same reason that LeBron leaving the Lakers would put them at the bottom of the table overnight. While knowledge sharing and thorough documentation is a way

The same reason that LeBron leaving the Lakers would put them at the bottom of the table overnight. While knowledge sharing and thorough documentation is a way to mitigate risk, I don't think it will ever address the loss of an impactful person's vision, knowledge, work ethic, etc... Sometimes other people will also lose morale or see it as a chance to leave themselves... It also takes considerable time to onboard a replacement, which can drastically affect timelines/budgets/etc...