He acquired a goalie that's not even in the same stratosphere as the one he let go. Korpisalo has better numbers this year? Great, I never wanted to see him play in Ottawa again. Ullmark not doing it yet? I'll wait, because he's show over the course of his career that he can do it.
What is it you want to know? Like, seriously? He gave up a late 1st and a 4th liner that Ottawa had soured on for one of the best available goalies in the league and then signed him. It's not working right now? So be it, I'd do that trade a thousand times over again.
Nevermind this rebuild is over or not over rubbish. It's over when the team makes the playoffs. Same goes for Detroit.
EDIT: It's the same reason Yzerman dumped all that money into Copp, Compher, Rasmussen, Tarasenko etc. You try to improve and sometimes you take you shot and miss.