The team is allowed to be 10% over the cap before the season. That freed up cap space went to Gus/Tank. It would have been cheaper to keep Walman and Sprong.
I'm just assuming Walman got caught peeing in the zamboni trough, because it's the only logical explanation.
For better or worse, Yzerman is big on personality and once he doesn't like you, you're out the door. Walman did something that made Yzerman dislike him. A few guys on the team- Larkin- seem to have probably felt similarly to Stevie Y. At least a few bits of evidence point to it being related to Walman struggling to come back from injury and the team feeling that he could have tried harder, wasn't as injured as he made out to be, and/or didn't work through the pain well enough when in the lineup. Perhaps he had too much fun on vacation in Tampa too. Perhaps there's something totally unrelated that we never even got word of- the proverbial zamboni trough piss.
My personal opinion is that this was ridiculously stupid regardless. We had a ton of bad defenseman to get rid of, and we chose one of the good ones. We moved him at a time when he had no value and in an apparent panic. If we did this that fast because we can't tolerate having someone we don't like on the team dress for us, I think that's a little immature, but I do understand how important team buy-in can be. If someday we're in the playoffs and we're watching every guy give every ounce of their being to will the team to victory, that will be a nice consequence of this mentality.
The more worrying notion is that perhaps this was done to free up cap space in a desperate gamble to acquire Jacob Trouba. He's another washed up echo of his former self that we should know would be an immediate disaster on our blue line in anything more than a third pairing role (like every defenseman we sign/trade for). That notion terrifies me most of all as it indicates this "bring in bad defenseman" strategy isn't the "there's no sense paying assets to bring in good defenseman before the kids are ready, so we'll acquire stop gaps from the bargain bin" strategy that we delude ourselves into believing it is. Trying to bring in Trouba implies that Steve Yzerman watches Jeff Petry, Ben Chiarot, Justin Holl, and Jacob Trouba play defense and says to himself "oh yeah, I want more of that on my team." If so, this team is doomed unless our prospects just turn out to be so good that we never acquire pro scouted defenseman in the Yzerman era. It doesn't matter how much buy-in you get from garbage players. They're going to give you garbage results.
Regardless, the final result is that we have a terrible defense having lost our second best defender. Edvinsson has fortunately managed to succeed being thrust immediately into a top pairing role with some of the hardest minutes in the league. Unfortunately, Petry and Chiarot on the second pairing together have not faired nearly as well.