Why didnt the uchiha clan fight itachi back??!
Question: there have to be strong people in the clan
Answers: there have to be strong people in the clan
THEY DIDNT EXPECTED HIM.IT WAS A SUPRISING ATTACK!!!
they probabaly were not expecting him to attack he might have surprise them and when they found out there numbers decreased then killed the rest with mangekyou
he is too powerful and gifted
itachi prob. had a "anikan skywalker/darth vader" senario,was to strong in the force and turned bad.
he had someone to help him
They maybe fought back but lost because Itachi got the help of the founder of the Uchiha Clan, Uchiha Madra. So since Madra is the founder he must be the strongest and have the most abilities with the sharingan making it able for him and Itachi to kill the entire Uchiha clan.