Jack manifold tries so hard to get someone to notice him, whether that be in a negative light or a positive one, he doesn't care. during Tommy's exile, he steals "hotter girl" (a fake girlfriend that Tommy built out of a jack o lantern and logs) from him, and rubs it in his face, desperately wanting a reaction from him.
he gets no reaction, Tommy simply does not care. Tommy is apathetic towards Jack before saying he can pretend to care, that he can lie and say that he does care. Jack says this will only make him sad.
Tommy and Jack are so tragically similar in the way that they just want to be recognized. they want to be seen, and they don't care if it's in a bad way.
they both try to get revenge on people for wronging them, but when Jack does it, no one seems to care.
if Jack manifold were the one to burn George's house down, he would not have gotten exiled. dream didn't exile Tommy because he cares about George - dream exiled Tommy because it was Tommy.
jack repeatedly tries to get revenge on people by putting clay in their houses and saying it's from dream, but no one ever cares about it. it's just a minor inconvenience for them.
Tommy is the scapegoat of the SMP - and Jack is the one that is always ignored.
they both try to get any type of attention, they're so desperate for someone to care. Tommy gets that attention, and he only realizes he doesn't like it after the fact.
jack never gets that attention.
jack sees Tommy getting all this attention, he sees him doing the exact same things as him but getting the result he never gets, and he gets upset.
during the season one finale, he specifically aims the nukes to Tommy's house. it's a desperate last attempt, maybe if he gets rid of the person getting more attention, he'll get the recognition he so very craves.
tl;dr: jack manifold and tommyinnit are so similar in a very tragic way and i have brain rot over it