The title here is a bit misleading. It should be "Why FitFinder never happened at UCL". It's a bit much to tar all of the UK with the same brush as one University.
I think it's a natural consequence of the site's increasing popularity combined with pg's constraints on new submissions. In particular the new page only has 30 spots and it's very easy at peak submission times to fall off. Whereas it used to take an upvote or two to make the front page, it now takes anywhere between 4 and 7 upvotes before you hit lots of people.
Your options (as a submitter) are either improve the content or improve the submission. Sometimes the latter is easier than the former, especially when it's your own material you're submitting.
