How to sequence events, one after another?

Looking for advice on this. How would you wait for an animation sequence and then trigger something, then trigger another thing, and so on?

For example, let's say the player wants to throw a fireball at an enemy. It should cast a spell with an initial player animation, then create the fireball entity, then the fireball should follow the target pointed at by the player initially, then it should explode and make damage to all the entities around the target.

A comment that got me thinking about this: "I really, really like to code all that stuff in one place in code that looks something roughly similar to that sentence above. But usually [with ECS systems in general] I end up with 5 systems, 5 components, everything decoupled and there is no way to see how the fireball will actually fly, without knowledge of all the systems in the game."