Answer: Your hypothesis could be wrong in another sample
Explanation: if you take a particular event and make a theory from it, this theory will have specific characteristics, causes and effects that won't be accurate in other samples.
For example, if you take an event that happened in a small town, this event will have specific variables that are attached to the fact that it is a small town (small population, particular economy, different culture and rituals, and similar issues). If you make a theory from it, and then you try to apply that in a big city, it is probable that the result won't be the same because the city has a different dynamic.
Generalizing theories need to be tested a lot of times in different scenarios, and each time the result has to be the same.