A lot of teams look dumb in hindsight with what happened with Vegas. Just look at the Panthers. They traded Reilly Smith to the Vegas Knights for a 4th round pick and in doing so agreed to let the Knights take Marchessault in the expansion draft. It was done for salary purposes... but seriously, how the hell does that look now lol.
McNabb was a bottom pairing guy with Kings. It would be very difficult to argue with a straight face at the time that the Oilers should have acquired Brayden McNabb, a left shot 15 minute a night d-man on a non-playoff team, and protected him in the expansion draft. Doing so would have required the Oilers to either expose one of Klefbom or Larsson on defense or go to a 4+4 protection and leave a guy like Maroon or Eberle available. It would have been an insane suggestion at the time.
I agree with the premise of your post though. There are good d-men out there who are available every year. A shrewd GM needs to be able to identify guys who can come in and contribute beyond the cost it takes to acquire them.
Unfortunately Chiarelli is 0/2 on that front. Not only is he unable to identify the right "just needs a chance" guys he also pays through the nose for them.
McNabb is a 3-4 D on a lot of clubs. He's top 4 in Vegas. Of course LA has Doughty, Muzzin, Martinez so the guy would have to be miraculous, allstar material, to be any higher slotting in in LA. He did get a lot of top 4 assignments in LA and had two strong seasons prior to even last season. One year he had 25pts and without a lot of time on the PP. Last season McNabb was out afairc with injury and his absence hurt the Kings.
The Kings didn't want to lose McNabb outright. The talk was they wanted Vegas to pick Brown (could you imagine?) or Gaborik. Had the Knights picked Brown they would have looked like geniuses with his turnaround season but McNabb was no slouch.
What the Knights got immediately is a big mean moving traffic D with all kinds of Willy Mitchell game in him. He's a fierce competitor and balls up all the time. He was 26, seasoned NHL experience, ready to unpack. Buff/LA had done all the development years on the player.
Thing is that McNabb is just one of many key ingredients the Knights brought in who can certainly play hockey but can certainly intimidate as well. He's a bonecrusher with hits. tbh I liked him in LA more than Martinez. McNabb can really get in opponents heads. Even going at guys like Doughty and Kopitar.
But its just one story. Every D the Knights have came ready and able to play. Just solid additions.
Its kind of karma fitting that McNabb scored the series clinching only goal in the last game and Martinez did little but give up scoring chances as the weak link top 4 D defensively in LA. Always loved Brayden McNabb. My kind of D.
In anycase the Oilers would not have had to protect Larsson in my plan because Larsson would not be here, Hall would. That should go without saying.