Things have changed in the last 4 years. At the time that the NCC and city reached out to the Senators, Cyril Leeder was driving the bus on this project, and he was spearheading the bid.
Leeder was someone with an incredible reputation among the Ottawa business and government community, and while he can certainly be criticized for some of the stale marketing and sales tactics the Senators used, he was the reason the Senators and Lebreton was seen as promising.
To navigate a project that involves federal government, local government, and corporate interests, you need someone who's well liked, who can act as a bridge between parties, who can resolve tensions, etc. Leeder was someone who could handle all the red tape and egos involved.
Melnyk is the opposite, as has been proven time and time again.
If Melnyk does want to salvage this? Bring Leeder back and put him in charge of this development from the Sens perspective. Fat chance of that happening though.