Most ecosystems in nature achieve equilibrium over time. Unlike natural ecosystems company culture ecosystems never do. The startup company ecosystem in particular is continuously in a rapid state of change. Whether the shock comes from the competition, employees joining/leaving, new financing rounds, new investors, government idiocy (Brexit) or the launch of new innovative technologies - they can all threaten the balance, even destroy the ecosystem or in some cases like the launch of the iPhone super charge the ecosystem.
The CEO's role is one of tight rope walker. Anticipating and adapting to the changes, thereby maintaining the balance while continuously moving forward.