How did Atticus explain Bob Ewell's provocative behavior in To Kill a Mockingbird?(Chapters 23-25)Why do you think he told this to his children?

I think that the answer you are looking for in at the
start of Chapter 23.  There, Atticus says that the reason Bob Ewell is acting like this
is that his pride and credibility has been destroyed by the trial.  If he does not do
something to fight back, he will lose respect for himself and maybe people will look
down on him even more.

I think that Atticus says this for a
couple of reasons.  First, I think he wants the kids not to be afraid.  Second, I think
he wants them to see all people, even Ewell, as people who have valid and understandable
feelings.  He wants them to stand in the other person's shoes and understand their
outlook.