To be clear, this all hinges on an explosion from inside the pipes - which should be something a forensics team can determine. As I understand it, the broken portion is in 250' of water, so an inconvenient but not impossible environment for forensics. There are also pipe laying ships that can bring pipes to the surface, the problem there is that moving the pipe could further disturb the scene, and potentially leave any remnants of whatever device (internal or external) behind on the seafloor.

It's a decent theory in that is covers a lot of 'whys' and 'hows', but I'm waiting until more is known. About all that seems certain is that the single party with no advantage in doing it is Germany.