why did Matthew ?
Why did Matthew help four?
The only clue to this is when Nita told tris "you're not the only one who hate David"
But it's very far and Nita say it after Matthew help Four
help... anyone ??
shareI haven't read the books and maybe the reason is clearer in them, but I got the impression that David's system was just another dictatorship - and he was no different to Jeannine and Evelyn. Plenty of people are aware of what he's up to, but they go along with David because the alternative is being killed or worse.
But Four and Tris are notable to the others. They were able to bring Jeannine's system down and encourage a rebellion. So Matthew realises that the best chance of changing the system is by helping Four. All he can do is warn Four that he's walked into a trap. So Four gets a headstart back to Chicago and Matthew can warn Tris that David is dangerous.