How is it on other Stack Exchanges it takes multiple votes to close a question, but on Space Exploration one person has the power to close a question even if it is not requested by others?
Muze, all Stack Exchange sites have moderators to supplement the community. A moderator has the ability to perform what we informally refer to as an "insta-close", which immediately closes the question with only one close vote. The community has the ability to override this if they desire by voting to reopen. Many of our users may simply not have the time to read through your long question to see if it is worth closing, that is why we have moderators who volunteer to do this type of activity. For what it's worth, I fully support Kim's action, and I was about to send you a private message anyway.
Also, the moderators are audited by the Stack Exchange Community Team (who are employees of Stack Overflow), and if you have a complaint about a moderator action you can email the Community Team at email@example.com.