IMHO its because it wasn't one person posting pictures at the time you closed it. There were several regular contributors at that time, even if there had been points when it was only @wtw. Also, probably because you were/are the only mod to noticeably take an issue with it. And given that @CalBear had actioned a user but not closed it the thread it did seem a bit like you were jumping on an excuse to close a thread you didn't like. And since you asked for a Help and Rules thread about it here we are.
Actually I didn't close it ONLY because BKW had ruled that it was acceptable when it was initially created and in general the Mods are loath to overturn each other. I've rather disliked the thing from the word go and would have closed it straight out of the gate with a couple really snarky comments had BKW not ruled to the contrary.
The original purpose of the thread was to discuss what fetishes people have or had heard of and why those fetishes might have arisen. It was never meant to be entirely serious, of course, but the idea was to have an interesting conversation about the (armchair) psychology of fetishes. Why do some people like feet? What drives a person to whips and leather? That kind of thing. It quickly devolved into the "Official Pics of Gorgeous Women In Latex" thread soon after it started, though, and that was that. I'm honestly surprised it wasn't closed sooner.
My point is that the majority of the content in the Fetish Thread (the "softcore porn" as Burton says) could have been posted in the generic "Official Pics of Gorgeous Women" thread (and almost certainly belonged there). Because it wasn't, we basically ended up with two threads functioning in the exact same way.