I think it's nuts that a team wouldn't give up Glass, two firsts, taking Ryan's contract, and a conditional pick for prime Karlsson. Vegas was red hot this past season. If Karlsson wouldn't sign, they could easily flip him in the off season and have gotten not all but a big chunk of what they gave up back.
Maybe I'm just too close to it as a Sens fan, but the opportunity to acquire a player like Karlsson is very very rare. Let alone the opportunity to acquire him for a team that was red hot.
So if Vegas gave up that package, they end up in three scenarios...
1) They only get one playoff run out of Karlsson, they do this when they are the hottest they might ever be for a long time and increase their odds of winning a Stanley Cup, which is a very hard thing to do. (With the benefit of hindsight, we can add that they probably would have won the Cup with Karlsson....but we didn't know that for sure at the time).
In the scenario above, the probably are able to recoup a big chunk of what they gave up for Karlsson by trading him in the off season. They won't get back the equivalent of two 1sts+Glass+Ryan's negative value, but they should be able to get enough draft picks to largely make up for everything they gave up other than Glass. If Karlsson will sign elsewhere, just not in Vegas, Vegas probably gets back similar value to what they gave up, just different pieces.
2) They extend Karlsson, and have the best defender of this generation (Maybe Dahlin will overtake him) locked down for the rest of his prime, and all they had to give up was an exceptional prospect and some draft picks that they could recoup by trading other veteran players if needed.
3) They keep Karlsson for two playoff runs and lose him to UFA. Maybe they win the 2018 Stanley Cup.
To me, that's a gamble Vegas has to take. The upside of the trade was just too high, I can't believe they didn't do it. Looking at the situation above, it makes me think that maybe they thought Dorion had less leverage, and that he'd crack and take their best offer, but it never happened. I just can't see why they didn't pull the trigger.