I wonder why there is so much controversy about whether or not astronauts really landed on the moon. ABC news is about to show some enhanced video that makes it easier to prove.
I've wondered this too, but it might be more accurate to say, "why is there so much visibility over the minority of whacko's who are in denial of the moon landing", because there's no "real" controversy at all.
My guess is that the visibility of this particular conspiracy theory arises from pure entertainment value. People are entertained by controversies, and this one is very colorful. Also, it hinges on arguments which relate to the scientific understanding of the moon, and of space. And most people are so woefully under informed in scientific matters that they can't immediately differentiate between paranoia and actual data.
There is also an atmosphere of distrust working here. Many people distrust the government almost by default, so they give consideration to things which play on that distrust. This is also interesting because skepticism is a healthy thing, but here we have people being overly skeptical of the government, and much less skeptical of the crackpot ideas they are being fed. Why the discrepancy in who to be skeptical of? The pre-defined distrust of government seems to over ride the healthy skepticism that should be applied to the crackpot theories. Hmmm.