This Question was closed as a dupe by Community and pxeger, but why Community and how did Community know?
The challenge author voted to closed it as a dupe
See this MSE post: New UI encourages askers to confirm or dispute duplicate votes
Essentially, when a user votes to close a question as a duplicate, the author is shown a pop-up that says, roughly:
This question may already have an answer here:
[link to potential duplicate]
and they are asked to decide if that question is indeed a duplicate. If they click yes, they instantly close the question as a duplicate, and the vote is attributed to the Community user.
Note that if you hover your mouse over the Community user's name, it provides a helpful tooltip: