One answer: Duncan is insightful, respectful and shows moral order for the little time he has in the play. Another: Duncan is far from insightful: he is astonished by the treason of Cawdor ("He was a gentleman in whom I placed an absolute trust."), chooses the feckless Malcolm as his heir instead of the better-qualified Macbeth, and is oblivious to the resentment Macbeth feels over being passed over. He is a good man but not a very good king.
why was macbeth releuctant to kill duncan
The night of Duncan's murder he is spending the night at MacBeth and Lady MacBeth's castle.
"I" said Macbeth, "with the servants' daggers. I killed Macbeth."
He kills the chairman, and he admits it saying he did it out of rage, scaring Duncan's sons more.
Duncan and Macbeth are cousins. Therefore, they are bound by kinship. They are also bound by subject and host, as Macbeth is hosting Duncan as his guest.
Macbeth was a loyal vassal of King Duncan. Macbeth's act should not be considered regicide.
Macbeth kills Duncan's grooms after Macduff discovers the body.
Macbeth kills Duncan in his own castle at night time.
They were killed by Macbeth because he blamed them for Duncan's murder.
Macbeth stabbed him when he was asleep.
The reaction between Lady Macbeth and Macbeth is initially very different after they kill Duncan. Lady Macbeth is enthusiastic but Macbeth regrets his actions.
To inherit Duncan's Throne