This.
An NBA roster has 12 guys max, 7 or 8 of whom generally play regular minutes, it's much easier to substitute tactically at dead balls to get the right match ups, and the best guys play 90% of the game. If you've got 3 guys that can dominate, the rest of the guys can be replacement level and you can win championships.
An NHL roster has 23 guys max, 19 of whom play regular minutes, matching up on the fly can be a nightmare, and the best guys get maybe 25-30% of the game. If you don't have 3 solid forward lines, 2 solid pairings and a pair of decent goalies, you're probably not even a playoff team.
I haven't watched the Oilers enough to know what their depth is like, but obviously they're paying so much for their top 2 guys that they can't possibly have enough to fill out the team. Seemed like they were getting away with it before, and now they are definitely not. Fascinating.