Dhruv as a character has always been guilty of tunnel vision.. that is simply a direct effect of his stunted emotional range.. his disease, his sheltered upbringing and Manik's over-protectiveness has always kept him from facing the real world on his own or feeling the pressure of having to make his own decisions.. therefore he simply focuses on whatever holds his attention at the moment or rather acts upon his dominant feeling without too much deliberation.. he is not capable of mature, faceted thinking..
When his focus was on Manik then it was all about him, their 'buddy' relationship, he had almost no individual interaction or any kind of bond with the rest of the Fab4.. Once Nandini entered the picture and caught his attention with her courage and free spirit then it suddenly became all about her.. that is why during the goons incident inspite of knowing Manik so well, it didn't even occur to him to consider Manik's POV.. he saw it all only from Nandini's side.. When Alya told him her version of events, he saw it only from her perspective.. His thinking is unilateral, he is incapable of nuanced understanding.. when he decided to end the friendship with Nandu, it became all about Manik once again... after that he wasn't thinking about her anymore hence his lack of his reaction when she got hurt.. then when he started to believe he was in 'lou' with Nandu (courtesy Alya) his tunnel vision became absorbed on that.. he longer noticed the recent glaring, drastic changes in his buddy's behavior, he didn't even notice Nandu's own sudden interest in Manik, he was too into his own perspective at that time.. so much so that until Nandu's final rejection happened, he didn't even notice Alya's tears, her discomfort regarding the accidental kiss, her developing feelings towards him etc none of it. Until she pushed him to acknowledge it but once that happened, once again it became all about Alya.. hence he had no reaction to the MaNan revelation but he was very miffed by Alya's reaction to them.. the dam bursting on his insecurity is also a function of all his frustration with Alya's mixed reactions.. he cannot understand her because he's incapable of processing ambivalent emotions.. either you move on or you don't.. things are either black or white.. "in-betweens" are a novel concept to him and so he feels betrayed by Alya's back and forthness.. Now he is focused only upon himself and his own view of things..he is angry because the world is more multidimensional than he realizes and he feels confused, frustrated with his inability to deal with it all.. even worse, his tunnel vision prevents him from empathizing with or understanding anyone else's POV.. he feels cornered, overwhelmed and he is lashing out at anything and everything that crosses his path..
Manik, a helpless victim of his own savior complex has put himself in the line of fire simply by reacting like he always does.. to try and take responsibility, try to 'fix' it by enabling this tantrum, the very last thing someone like Dhruv would want.. to him it comes across as patronizing and belittling.. fueling his rage and false sense of righteousness even more.. and so the vicious cycle continues..
