It's mainly because each organization has its own sources, perspectives, and editorial policies. Different reporters might focus on different aspects of an event or interpret it differently.
Well, there are several reasons. First, news organizations have varying access to information. Second, their target audiences and political leanings can influence the way they present stories. And finally, competition can also lead them to offer unique angles to stand out.
The main cause is that news comes from multiple sources and gets processed differently. Each organization has its own agenda and biases, which shape how they report. Also, time constraints and the need to attract viewers/readers can result in distinct stories.