There were three potential winners in this arrangement: Seattle, Arizona and even Schofield.
A quick look at some of the dynamics for each of the involved parties:
Cardinals: Schofield was scheduled to earn $1.3 million in the final year of his rookie contract. The team had just signed veteran pass-rusher John Abraham to a two-year contract after determining in its judgment that Abraham was still playing at a high level. Schofield carries a high risk for injury. Had he gotten hurt, the Cardinals could have been on the hook for the full $1.3 million -- after adding Abraham, who figures to take away snaps from Schofield. By cutting Schofield, the Cardinals were basically indicating they didn't necessarily expect to keep him beyond the 2013 season, and they thought his salary no longer aligned with his value relative to the risk.
Seahawks: Seattle has short-term depth issues at defensive end and outside linebacker while Chris Clemons recovers from injury and Bruce Irvin prepares to serve a four-game suspension. Schofield is 26 years old and was a player the team valued in the 2010 draft. The Seahawks, like the Cardinals, cannot be excited about carrying a $1.3 million injury risk, however. Claiming Schofield off waivers meant claiming his contract, too, but we should expect Seattle to seek a streamlined deal featuring injury protections for the team. Giving Schofield a chance to earn back the lost salary would make sense as a reasonable tradeoff. Schofield wouldn't be able to command $1.3 million in the market after suffering a torn ACL (2010) and broken ankle (2012).
Schofield: The manner in which the Cardinals released Schofield had to hurt. Schofield was about to take his pre-camp conditioning test when the move was made. He was pulled from the practice field unexpectedly and in front of teammates, a rough way for a well-liked player to go out. On the positive side, Schofield gets a shot at his former team twice a year in NFC West play if he earns a roster spot. He joins a team with Super Bowl aspirations. This can be a "win" for him in the end if he plays well.