Consider the timing...

Background
Operation Wigwam  evaluated the detonation of a Mark 90 Betty, a nuclear depth bomb.  The test was conducted May 14th in 1955, some 500 miles southwest of San Diego.  OP Wigwam results helped determine (see declassified Wigwam film) the effectiveness of deeply detonated nuclear weapons (nuclear torpedoes and depth charges, for example) in combat against submerged eneny subs.


What prompted Operation Wigwam to surface at 'War Is Boring" in December of 2014?


First, we know that nuclear tests are conducted and evaluated with limited publicity and nil transparency of results until declassified decades later:

"The bomb was suspended by cable from an unmanned barge and detonated at a depth of 2,000 feet in water that was 16,000 feet deep. The test had a yield of 30 kilotons. ...

In 1980, when the details of Operation Wigwam became publicly known, Governor Brown of California issued an immediate call for the federal government to publicly release the names of all servicemen involved in Wigwam, so that they could receive suitable medical treatment."  source

Additionally, tests, capabilities, limitations and ceetain operations applicable to specific U.S. submarines are justifiable secrets kept from public knowledge for significant periods of time.
Wigwam participants had to sign 25-year nondisclosure and secrecy agreements. Since all submariners had already signed some form of secrecy agreement beforehand, it was also necessary for many to sign non-travel agreements to certain foreign destinations for x years after their discharge from active duty.


More Recent Events

North Korea Is In The Process Of Developing A Fleet Of Nuclear Missile-Capable Submarines

In October, US General Curtis Scaparrotti, the commander of US forces on the Korean peninsula, warned that North Korea had developed "the capability to miniaturize a device at this point and they have the technology to actually deliver what they say they have."

In addition to submarine and WMD ambitions of known and suspected bad actors like North Korea, there have been unprecedented programs to acquire updated subs by nations dependent upon oil for food and energy shipments in an age of piracy, crime and Russian imperialism:

Global Submarine Proliferation: Emerging Trends and Problems

"Russia continues to be an active exporter of finished diesel submarines and is now providing nuclear reactor and submarine-design technology to China and India. In the Middle East and elsewhere, Germany remains a major submarine exporter, despite the WMD potential of some of its clients."

 In Molten Eagle's opinion, the How to Nuke a Submarine article by War Is Boring contributor Steve Weintz is a very timely reminder to potential bad actors of a severe, unexpected vulnerability to any injudicious acts they may have planned.  Like India (unfortunately) the DPRK has decades of catchup to overcome.

Submarines are always silent and strange.