The D was Steve Finger's idea after he came from P&W to be President of Sikorsky. He wanted the S-76 to have P&W engines not Turbomeca engines and the D Program was born. But Sikorsky was busy with the in service reliability issues with the S-92, the "what to do with Schweizer" question and the where to do completions the S-70i question.
When the GFC hit, nearly all funding was cut from the D Model, Steve Finger had gone back to P&W and Jeff Pino had little enthusiasm for Finger's project. To be assigned to the D Program was like being told that the next step was chasing parts followed by being shown the exit to the building. Being assigned to the D Program Management was seen as a punishment.
There were (are) some great talented people who made great progress with the D, the trouble is that they were not properly resourced with $ or people. The oil and gas industry, one of the historical S-76 customers, had moved on to the AW139 in spite of some issues. The lateness of the D meant that it was (in terms of size, cabin and crashworthiness) out of date before it was even flown.