Nate definitely had to go. You cannot have $20m on three defensemen and $12m on goaltenders. But I would have rather traded a third than receive a third round pick from a division rival that nearly beat us in Game 7.
For those arguing trade Martinez +, Alec has an expiring contract which is very valuable with their current situation. With all the defensemen ready (I.E. Whitecloud & maybe Hague) and almost ready (I.E. Coghlan, Schuldt, Korczak), need spaces to open up. Alec is great for now, but his space will be valuable later.
Nate just isn't really a top pairing defensemen, especially for a cup contending team. Very solid second pairing guy. But we cannot pay him $6m a year with Petro and Theo.
As for Fleury, unless they were going to get some help from Ottawa or Detroit, it just didn't make sense to move him. If reports were correct, retaining 50% does nothing to help the cap situation. Keeping Fleury might help us next offseason. With the expansion draft coming, teams losing their goalie might see a need for Fleury as a stopgap. Also, this season will likely be very condensed. It will nice to have a "starter" each game.