He was probably considered since he is mentioned in the reasoning paper, still it could be one of those unfortunate omissions in the nobel history since those deciding the prize might have a hard time to measure impact.
So in this case they picked something that might be viewed as only having a tangential connection to the field, but the impact has been so immense that they probably went outside their regular comfort zone (and how many prizes can we give for LHC work that really don't touch regular human lives in the foreseeable future anyhow?).
I recently watched this quite video on the subject: https://youtu.be/zS7sJJB7BUI?feature=shared and found it quite enjoyable.
His acceptance speech was about general relativity.
Also, I think the process looks fairly decent:
https://www.nobelprize.org/nomination/physics/
Gather nominations, make a shortlist, research the shortlist with actual field experts, present candidates, discuss, and vote.
And in 50 years you'll be able to find out who the other candidates were!
Trusted… by who?