The events of Chapter 2 happen because of what happened in the first movie.
By comparison, the John Wick films are so tightly woven together, the second film follows almost immediately after the first and we know the same will be true of John Wick: Chapter 3 – Parabellum.
The reason that the following installments are called chapters is because they really are just pieces of a longer narrative.
Each event that happens follows directly on the events that came before.