From the BBC, mainly because of over-supply of ships, but also:
The Panama effect
And there was another reason to buy – and to buy big: the Panama Canal.
Last year it got a serious upgrade. The old locks could take container ships up to only 5,000 TEU (Twenty-Foot Equivalent Unit, roughly one container). These are known as Panamaxes.
But the new locks, with gates weighing 700 tonnes or more, are designed to take so called Neo-Panamaxes. These are giants, equivalent to the width and length of three football pitches laid end to end, and can carry about 13,000 TEU.
So shippers looking to carry cargoes from Asia to the American east coast ports, can now take Neo-Panamaxes through the new canal – and sell off their smaller Panamaxes. That's why Panamaxes like the Hammonia Grenada are going cheap – in fact, they're going nowhere…
Hitherto, from the point of view of Chinese exporting to Europe or the US, they were pretty indifferent between using the Suez Canal (simple, cheap to build and maintain) and the Suez Canal (stupendous and expensive feat of engineering), so the tolls (largely rent to use that location) which either canal could charge was roughly the same.
Assuming people prefer using larger ships, whichever canal allows larger ships is obviously as a huge advantage and can charge extra tolls, but this suggests that Suezmax ships are still slightly larger than Panamax ships, in which case the Panama Canal has miserably failed to leap-frog the Suez Canal in terms of size, but nice try anyway.