First things first, does Zellsis have a history of slamming desks in ranked matches when the outcomes don't really matter? Has he displayed a pattern of toxicity, including using slurs and behaving poorly towards other professionals in the scene? (https://www.youtube.com/watch?v=nhPtOQwgvpI).
It's not just the sighing that indicates a mentality problem; it's the consistency of his behavior. While one instance of poor behavior can be forgiven, when patterns form—such as in the clip showing him being toxic, sighing, and getting extremely tilted in ranked—it's indicative of a deeper issue. At the start of the event, he also stated, "There are no good teams in this event. The level of play is low."
Regarding your point about "overemphasis," I mentioned both Bang and N4rrate. However, I can only comment based on what I observe. I haven't seen Bang do anything problematic, which is why I don't have concerns about him, but I do regarding N4rrate.
I never claimed that this was the primary reason for the team's poor performance; I clearly stated that I believed it was "a problem," not the sole reason for their struggles. I also emphasized that "this situation is different because there's a genuinely personal issue on N4rrate's side that needs to be addressed." This issue isn't solely about Sentinels; it's personal. However, it can still impact games and scrims, affecting how other players perceive his attitude.
It's important to remember that when there are five people on a team, and all five are trying their hardest, they can lift each other’s performance. But if one individual keeps getting tilted, calling others "braindead," trolling, and being toxic, it can seriously hinder the motivation of the rest of the team. The same concept applies to a professional team. Their mentalities may be stronger, but they aren't immune to these issues.
"This was never mentioned during his time at Karmine Corp." While it matters how he is acting on Sentinels, the focus should be on his current behaviour rather than how he behaved at Karmine Corp. If you want to argue why it may not have been brought up, it's worth noting that Karmine Corp has a long history of having seriously toxic ultras and fans in League.
I also agree with what #18 says: Zellsis shows that he is invested and wants to win that round. I've reacted similarly in my past games, but I've never intentionally kept my mic on to sigh into it. That is a conscious action, and at that point, you're just bringing down the vibes.
Edit. I wanted to add this as extra since u are clearly not convinced, I think it's fair to say Aspas has a good mentality and u can see the differences here.
https://www.youtube.com/watch?v=rKOaqhvwSVQ (N4RRATE)
https://www.youtube.com/watch?v=Dg34KQ9DVWU (Aspas)
Both DM vods, One is five minutes, one is 50 minutes and I guarantee you without watching Aspas' that N4rrate complains 10x more than Aspas in 5 minutes than Aspas does in that 50 minute vod.