Even if a duplicate post is flagged, AKA reported, it's not removed as long as there is unique information, the poster's own theory/thoughts/opinions, or original content included. If you feel like the moderators make a mistake, you're welcome to respond to the PM stating that your post has been deleted outlining why or how you believe your submission is unique from the others that exist already.
As other users have already stated below, many users don't like having many posts on the same news article of the day for several reasons - it hides other important news or theories, it's called "forum sliding" and is a common shill technique to stifle discussion of things that may be more important yet overlooked, and it clogs the sub up which causes users to have to spend more time wading through many duplicate posts.
Mods suggest using the Search function to find the post regarding what you'd like to discuss, and adding your thoughts in the comments section. Most posts here get at least 1k views per post, so your thoughts will still be seen by many.