Put the most important and newsworthy facts first, with least important and least immediate facts last — this is opposite to development order in typical narratives, and is termed inverted-pyramid style.
To help the reader, who is usually in a hurry when reading news. Putting the important and new aspects first helps since they may skip the story after only a couple of paragraphs.
To help people who are editing your story later. We appreciate stories with plenty of details, but we still like short punchy stories are preferable to rambling essays.
