There is no big secret about it, which is the sort of reason the Daily Mail is Fail. It's just not talked about much outside of the business pages - there's no conspiracy to kept the fact of the anchored fleet covered up.
There are two reasons for it to be there: one is that a glut in cargo ship availability (due to the long order cycle) has coincided with the recession, so that the expected growth in shipping has stalled. Hence the large number. As for the location outside Singapore, it's handily just north of the equator and so not subject to tropical storms and weather patterns, meaning it's the handiest place is Asia to park a ship without paying port fees.
Sure, it's interesting that there's so much unused capacity gathered in one place, but 'secret'? I think not.
