If he wiped out the Uchiha's with ease, the Hyuga would be a walk in the park. He could just control a bunch and pit them against the others.
No one is saying it wouldn't be easy, you dumbass kid...
If you're using plot and storytelling and not some random ass encounter then him killing the hyuga at that time would legit cause a war.
Konoha just lost 2 noble dojutsu clans in a single night.
Itachi wanted to avoid unnecessary bloodshed and another war, something the coup would have started. It aint shit for any village to roll over Konoha after that.
Minato dead.
Uchiha are gone.
Hyuga are gone.
Their weapon is inside a child.
Hiruzen is old.
J-man mia.
Tsunade mia.
That's a stark conflict of interest between Itachi and Obito. Sasuke is now in-between a war. Naruto is most likely killed, captured, or hidden. Konoha 9/10 falls because we know who was alive at that time.
Obito didnt want them problems with Itachi.