1. He didn't know about this till literally 2/3rd the way into the story, years after he defected to the villages biggest enemies for 'lol vengeance!' reasons. Despite being a tratior, they still went after him to get him back. That should have rang some bells in his head, if he had anything in his head at all at that point.
Question, how is he a traitor?
He did not leave to divulge village secrets, what would have known he was a preteen. They told him nothing, he left so he could get stronger and find out answers. I mean he became a traitor later, but we aren't talking about that part.
Also , again he doesn't care about those people. He just wants what he wants. You do realize some people don't care about comradery right?" they went after him " the fuck does that have to do with what he wants. They are people in his way, nothing more. Why would that have rang bells, people have always viewed him as a value an asset, the last of the esteemed uchiha clan, not a person.
2. If his clan didn't want to get bodied, maybe they shouldn't have been plotting a coup that would have triggered a civil war. That one of their brightest stars took them all out, and not any other forces of the village, should also have been a clue to sasuke. Granted, for most of the story, Itachi was a villain, only retconned later to 'secret good guy'.
" Why did you kill my family "
" they were planning to start a civil war"
" hmm that sounds strange let me go as.... oh wait their all dead so I can't ask them anything "
"it was for the greater good "
" why does that guy have an arm with uchiha eye balls"
"... it was for the greater good"
" I don't know how you expect me to believe you at this point "
"Wait how did you find all this information out"
" I talked to itachi after I left the village"
" so you are a terrorist"
" Thats they only way I would have found out the truth "
"Well you are a terrorist now"
" this sounds like a fucking set up "
3. He didn't care who 'cared about him' the dude had one goal: gaining power. He was willing to betray or doublecross anyone who couldn't provide him the fastest path to that. It was his choice to defect to the sound for power, to defect to akatsuki for more power, to attack Bee and the Kages, and even to try to assassinate them from inside their dreams. A pair of crappy events early on do not justify throwing everything away for power, time and time again. At some point, he was fully responsible for his own actions.
You are expecting people to react the same to things and to have similar personalities.
You already fucked up. You are expecting things from war torn people. You might want to reevaluate that, it would make life and literature a lot easier.