Here's my take:
- Eller's serious injuries occured because his face smacked the ice;
- Eller's face smacked the ice because he made no attempt to brace his fall with his arms;
- Eller made no attempt to brace his fall with his arms because he was knocked our by the contact
In my experience, getting knocked out by a full body shot where your head whips around just by the rotation of your torso doesn't usually happen; it's usually by a shot to the jaw ("on the button"). To me ,the video supports the latter, with Gryba's shoulder connecting with Eller's chin.
I also agree with Shanahan that it looked like Gryba made little effort to go shouder-to-shoulder, and either intended or made no effort to avoid making it a glancing blow across the front of Eller that made contact to the head much more likely.
Injury + shot to the head + little effort to avoid head = suspension as a reasonable choice, IMO.