I have nothing to back me up, but I believe that trade was a PC Hail Mary knowing his job was on the line. If he was denied, he'd have an argument that he should have another year. I think PC felt he was close to a playoff run and needed one chess piece. That trade was so out of character for the organization. I think it was JS/JA giving PC what he wanted knowing it was a final chance.
In the end, it was probably more expensive than anyone would want, but (if any of the above has any truth) it allowed the organization to move forward while still giving PC every opportunity...which he deserved.
Ironically, now LWilliams, BMurphy and JReed bring similar flexibility to MBennett, CAvril and RBryant. PCs fluid-architecture on the DL may be revived after his departure.