I've always thought the LWilliams trade was agreed by JS and JAllen to decide one-way-or-the-other on Pete. I don't think it's a stretch to say Pete was the eternal optimist and always professed the team was one piece away from a deep playoff run. I honestly think LWilliams was signed to give Pete the piece he said was missing. If it works, Seahawks are back on top. If not, no more excuses and the team moves on. We know what happened.
So...once that decision was made, JS goes to work re-signing LW and building the team with his personal/individual vision. It was a risk, but it also had the benefit of moving the team forward even if the trade itself didn't work.