From the video posted above:
Trade been in the works for a few weeks
Other teams seemed to want Lehner out of all the Ott goalies
It was difficult to part with him, but Anderson is their number 1 guy - top 10 in the league. Hammond stepped up and made Lehner available
Legwand was a big part of the deal to get cap space and free up a roster spot for their young guys
Feels they got an ok return for Lehner
They believe he will be a top goalie in the league and they didn't want him in Buffalo - they wanted him out west, but couldn't get the deal done
In a normal draft year they would have been far more reluctant to do this. This year they think they'll get a good player