Isaac Hempstead-Wright, who plays Bran Stark in the show, talked to EW about his character's new personality in the last episode of Game of Thrones:
"I think it’s a major shock for Sansa, she’s lost her brother once before when he fell out of that tower, and now Bran’s back but she loses him all over again. All the Starks have changed so much. Arya is like this ninja assassin. Sansa has been held captive by these tyrannical men and had to become politically cunning herself. But Bran is now this tree-raven-magic thing.
It’s like imagining you have all of space and time in your head. Bran is existing in thousands of planes of existence at any one time. So it’s quite difficult for Bran to have any kind of semblance of personality anymore because he’s really like a giant computer.
Bran really at this stage is not the Three-Eyed Raven. He’s got the title but hasn’t had thousands of years of sitting in a cave looking through time. Somebody put in front of him a massive encyclopedia of all of time and he’s only opened page one. He can look stuff up but doesn’t have this all-knowing all-seeing capability just yet."
David Benioff also said Bran is broken in more ways than one, "he’s got serious challenges dealing with all the stuff happening in his mind and that prevents him becoming this omniscient character."