Nate's "storyline" (as you put it - I'm guessing you are referring to
underdog becoming asshole ? ) /has/ been there the whole season (possibly part of last season I can't remember when they had the 'new towel guy' there but it started then) but its not a 'obvious and direct' storyline.
(ok I try to be as NON spoilery in specifics below but I have to allude to some of the character we're talking about so if you really don't want to know anything at all about it just skip the rest of the paragraphs here lol. But NOTHING SPECIFIC about events in the show is below.)
Nate's been having these negative comments/interactions only with certain other characters in the show, and not with others - but it has been more subtle - one or two comments/lines an episode - and then its never addressed/commented on further. We've been watching this personality trait of Nate's come out only with people 'under' him and in other snippets of interaction here and there - but you are right - its not really a 'main focus' plot. Its more watching a subtle personality shift come into play as a character develops, as a negative side effect of how his character has developed - and I've been really curious as to where 'this was going' and when it was going to come into the fore-front (clearly- now!).
For me - I've been more frustratedly waiting for anyone in the show to address this growing personality flaw in Nate. I expected the writers weren't just making these one-off lines for no point, but waiting a whole season (or more) to find out "ok when is someone going to say/notice something with Nate?" AHhh there it is.
But yea - the personality 'trait' for Nate that came to a head with this last episode has been something brewing in the background of the 'main character interactions'. Last night's episode was the first time they really 'brought it to the forefront' and directly shone a light on what he was actually thinking/doing. Prior to this episode, we've had his dialogue with certain underlings in the background but they never gave it any explanation or deeper context. Really curious to see where they go with this - because the subtle shift in his character - this 'one side of personality is XYZ but this other side is ABC' - could be something that ends up being brilliant with how they've written and executed it; or could be a dead-end.
And if that's not what you meant - nevermind
.