When Hikaru made the Sauron comment, he was being smacked around by Magnus but not at the level of total domination that was demonstrated a few years later.
I really believe that Hikaru had a genuine belief that he was somehow capable of beating Magnus in a match, but he later played it off as being trash talk when it was clear his honor and skills as a professional were being insulted.
I think Hikaru has been humbled, a bit.
I've seen him, on a few occasions, acknowledging that Magnus is superior to everyone playing these days. He's also admitted that he spends more time studying Magnus' games than the games of any other player.
I don't think Hikaru from a few years ago would've said these things.
Though I also would not be surprised if he were to once again declare himself the only challenger to Sauron, now that he's qualified for Candidates. 
you can respect someone's talent without liking them. Bobby Fischer was erratic and hated Jews. Henry Ford was similar. you have nothing to complain about Hikaru.
The big question is can Naka play well enough to win the most important event of his life? Streaming & playing a lot of speed chess can't be good prep for the candidates.
I don't know what relevance "like" has. Do I regularly watch his videos? No. There are much better explainers of chess than him to someone of my level, and I don't know why he has the annoying habit of reading an entire gossip article instead of giving a link and saying read it yourselves.
I will admit to rooting for him a bit at the Grand Prix just because he hadn't played an over the board tournament in so long and seemed to go in with a relaxed attitude. I listened to one or two interviews and he just sounded like a normal chess player.
One doesn't have to like a personality to appreciate them in the game. Hikaru is giving Magnus his only main challenge in Rapid and Blitz, so he's doing that for the game.
You can certainly call it my bias, but again, I think a champion has a few excuses. I think of it this way... when I lose a tournament game against a player who is clearly weaker than me, I'm upset. I don't mean a lower rated player, I mean a player who I can tell is weaker by their generally inferior moves.
For a dominating world champion (of any sport), this is nearly 100% of their games... so nearly 100% of their losses are painful... plus champions tend to be young, they lack life experience in general. So ok, they become upset. I think it's understandable.
In my mind this is very different from e.g. Hikaru being upset after losing to Carlsen. By every metric Hikaru is clearly inferior to Carlsen, so he doesn't deserve to be upset. It's just the natural order. Sure he can be upset for failing to play up to his own standards, we all have bad days where we disappoint ourselves, but e.g. the Sauron tweet isn't about reasonable standards, it's about blind idiotic arrogance.
It's understandable, yes, for Magnus to expect domination, and to get angry when he lets games slip away.
Though I believe Hikaru's tantrums get a bit over-criticized, too. Often, it's quite obvious that he's angry with himself, for missing things. Not necessarily petulant that he didn't win, but petulant that he didn't see things that turned out to be so obvious (to him) in post-analysis.
He's emotional. Competitive. Doesn't handle losing well. That's just who he is. I find him a bit Diva-ish, but hardly the "toxic" person that some players describe him as.
The way he's described, you'd think he's strutting around like the Connor McGregor of chess, or something, hurling insults and swear words at everyone under the sun ...
Also: Hikaru's Sauron tweet didn't age well, that's for sure.
Though I believe he was talking about his 2013 Sinquefield Cup performance (since his tweet came relatively soon afterward).
At the time, Hikaru was #4 in the world. And the Sinquefield Cup was the last real tournament before Magnus' World Championship match against Anand.
There were 4 SuperGMs in the 2013 Sinquefield Cup: Carlsen, Nakamura, Aronian, and Kamsky.
Aronian and Kamsky both fell to Carlsen. Nakamura was the only player to hold Carlsen to draws.
So it seems (to me) that Hikaru felt that he was the only top player who could go toe to toe with Carlsen, without crumbling. He saw Anand falling apart against Carlsen, and thought, "Well, crap, I held Carlsen to draws, no problem, just a few weeks ago. I guess I'm the only guy around who can handle Magnus."
Wishful thinking, yes. Especially considering their lopsided head-to-head record.
But I think the context of that tweet gets lost in the re-tweets. And the internet seems to have no intentions of ever letting Hikaru forget it ...
I didn't remember as many specifics as you, but yeah, I remembered the tweet came on the heels of one (or several) good tournament performances. At the time I interpreted it as a hollow declaration... as if he was trying to talk himself into believing it, or maybe motivating himself to work harder for it.
As for your point about Naka not being as bad as some make him out to be, sure. I'm particularly receptive to that idea as a person who has probably been too hard on him in the past.