Why did this event happen? why did the titanic sink?

The titanic sank because

#1: They hit an iceberg that scraped the side. Critics say that if they smashed head on they might have had a higher chance of surviving
#2: because it was thought that the titanic was unsinkable, the crews were not trained enough to deal with situations.
#3: the watchman didn't see the iceberg until to late

hope this helps