Earlier quoted context omitted.
Actually Hikaru would be (as of today) 6/8 among the Candidates in classical ELO, as the world #11 in live ratings. If anything, Hikaru is probably underrated ; he gained around 20 ELO points in the two Grand Prix legs. Like the OP, I'll disclaim being a Hikaru apologist; but he is world #1 in blitz and world #2 (briefly #1 this year) in rapid rating, which is why, for example, http://universalrating.com/ratings.php…
Who is he higher than? He's tied for last as of current ratings on the fide website, or does that not yet include results from grand prix round 3? (Which would put him ahead of Teimor and Duda, presumably) > seems his strategy is just to survive the openings and then try to outplay or flag people later on, which is a surprisingly viable strategy. This doesn't work when people are both stronger middlegame players than…
It's just not obvious to me that any of your statements about the other players being so much stronger than Hikaru are true. It's really hard to objectively estimate his classical playing strength because he just didn't play for two years and the rating has been volatile since he started playing again, but (for example) he played 4 classical games with Levon Aronian between the two legs with a +1 -1 =2 score, and +2 -0 =0 in rapid tiebreaks. Aronian is a roughly 2780 player, world #5, likely to be the strongest player who missed candidates. Hikaru also scored 50% in classical Grand Prix matches with Wesley So and Shakhriyar Mamedyarov, two other strong top-10 players.