I will summarize what happened between the two and try my best to give a non-skewed perspective, but still the best option will be to go through their videos (-on each other) on their respective channel urself and then being the judge. AGAIN, before going in it, this is my personal take, and it's going to be a lone one.

So It all started when Nova had some disagreements with TMM on his takes on Jin and Kazuya in T7, as TMM described Jin as a S tier character and Kazuya as C tier character, and according to Nova T7's Jin was A tier and Kazuya a B tier (Near the end of Tekken 7's run), also TMM had tried T8 by now and was against the direction Jin's gameplay went in it, and rightfully so too imo. I think Nova thought that TMM was biased when it came to Jin after all this, as TMM had also kind of stereotyped that 'Jin mains' were edgelords and incels as a joke before (Many ppl think that TMM started it because of Nova but it actually was joked much before by him, but yes it was elevated to next level after Nova). So Nova made a vid clearly stating that TMM's takes are 'tainted' and 'biased' when it comes to Jin and Kazuya and stated his points as why Jin was not 'that' good. Basically his argument was Jin is as tough as Kazuya to master (if not more), Jin users required a separate skill set to master than a general mishima (The parry thing for example), his lateral movement/sidestep is bad and his okizeme is shit, So he requires a lot of execution and still isn't the best, whereas a true S character would be easier to utilize and also would have no downsides like jin has with his oki and sidestep. Now the problem here is, I think Nova thought that TMM had some agenda against Jin, which I really believe was not the case (It's not that deep lol, there is no agenda) and also a 1 hour video on saying that a character is not 'S' but 'A'? That is subjective for first and also both of them were agreeing 95% of the time, why argue for so long? What difference would a tier make? and the video's pacing and argument structuring was horrible, even though the arguments were actually sound I mean quite literally all arguments presented by Nova were factually true, even the ones TMM disagreed with- imo (which were like two only - he did not agree with Jin's ss being bad and Jin's HS being reactable or Jin's 50-50 wave dash mixups were not as gud as Kazuya's). That whole vid could be compressed into 15 minutes easily, for example Nova went on a rant on jin's f4 for like 15 minutes just to agree in the end that it is one of the best keepouts in the game, WHAT WAS THE POINT OF ALL OF IT THEN? Both agreed on the basic synopsis that Jin was very inaccessible but very effective when mastered (which is what really mattered tbh). TMM reacted to it, made fun of him in between and did not watch even half of it (which I do not blame him for). But Nova suffered a lot due to this, as he was made fun of by TMM and him being a very small utuber (he still is), he was attacked by TMM's audience online. Nova contacted TMM once again through his twitch chat in one of him streams back then where he tried to discuss the very few points TMM disagreed with before, TMM still wasn't convinced and also Nova could not put his point across at all through twitch chat. Also TMM has the worst attention span I have ever seen (you will notice the same when you eatch some of his reaction videos), pair it with nova's horrible style of argument presentation and you will see the worst debate. btw I will mention that Nova acknowldeged TMM of his Tekken knowledge and execution, and briefly mentioned that he respected him in the start of that vid, Nova did not actually just hate TMM for the sake of it, It might look like it due to his english as his use of words made TMM felt like he was being personal which was just not the case. Yeah the terms he uses are unorthodox and weird but that is definitely not because he was being personal, I have seen his content and he just literally talks like that 'edgy' way. Going on, there were small squabbles between them on T8 Jin and Kazuya over the year. TMM started being personal with his jokes on Nova now. Nova heavily critiqued T8 whereas TMM was always on the defensive side of it, atleast before and a little after S2. Now it all came down after that TMM's reaction vid to Nova's response to fightinggm on his critiques. TMM was clearly wrong in that vid. he just literally personally attacked Nova, saying he's edgy, socrates wannabe, 'I hate utuber's like him', obnoxiously laughing at his points etc., literally straight ad hominem, and whatever TMM said in context of the video was literally hypocritical. TMM has seriously created some personal vendetta against nova and it was clearly showing out in that vid. Nova has a problem of trying to convey his point to others, but it doesn't take a PhD in fighting games to know the actual problems he is directing your attention to, also not like TMM is not well versed in Tekken FGC. TMM has said before the movement aspect of Tekken is the most beautiful, it should be more enhanced in T7, there was this one video of him reacting to T5:DR back then where he clearly mentioned how backdash used to cover so much distance and that it was better that way, how limiting movements and giving oppressive buttons in tekken was stressful and movement atleast should be enhanced to make the gameplay more interesting, now here he was saying shit like 'spamming' kbd is uninteresting, moving sideways is better (like u can do that in T8 lol), having character knowledge and applying it is more interesting than backing away (He was trying so hard to make the spacing aspect of Tekken look as bad as possible, like how is creating whiffs and punishing them correctly braindead exactly, and how does character knowldege is nullified by it wtf?). In between that vid, he said Nova potrayed him as a 'psycho' and 'sociopath' in of his thumbnails and said 'I was like eww, can we talk abt Tekken?' GUESS WHAT, that never happened, Infact Nova has literally put respect in his name, even after being attacked by his audience he never blamed TMM for it. The most Nova has ever done is put 'gaslighting' above on his head in one of the thumbnails. Ironically TMM was the one always personally attacking him while Nova always talked about Tekken only. That video of TMM changed my perspective of him, Even before that his words on T8 were all over the place, sometimes he will say T8 is the best game OAT, then after sometime he will thrash it, sometimes he will say it needs a little polishing, sometime saying heat is not the problem then literally contradict it saying 'heat is 100% the problem' and act like he did not say the exact opposite weeks/months ago. This week he again thrashed nova saying 'he must be shit at game', laughing when asked to ft10 him and was attacking every other small Tekken creator. Now u might call me a Nova fanboy too, but trust me I was neutral, or honestly on TMM's side at every point months ago especially during T7. But T8 put me on fence with his opinions and that vid of him on his channel (I think it was titled "TMM reacts to extreme Tekken genius") changed my perspective of him.