In this tragedy, the reason for Macbeth's death seems to be because of the misleading predictions of the witches and pressure of Lady Macbeth. However, I think the main reasons for Macbeth's downfall and eventual death come from himself. He blindly followed his wife, he constantly alternated between his split nature, and his rationality was overthrown by his superstitious beliefs. Macbeth didn't analyze his wife's word and accepted all of it without any consideration. After Macbeth met the witches, although the witches said he will be king in the future, he never thought about killing king Duncan. When he spoke with his old friend, Banquo, he still felt loyal to King Duncan, (Act 1, Scene 3, Lines 128-158). After, he met King Duncan, he was really mad that King Duncan established his eldest son, Malcolm, as the prince of Cumberland, (Act 1, Scene 4, Lines 48-53). When he went back to castle and calmed down, in his mind, he still didn't want to do the evil thing, (Act 1, Scene 7, Lines 1-27). However, everything changed after his wife talked to him. He didn't analyze his wife's suggestions and accepted every single word which was said by his wife. I know a wife for a husband is like a heart for a human, which is the most important part in their life. But when our heart goes wrong, we can't let it continued to work. Instead, we need to have an operation to fix it, if we can't fix it, in order to keep our life, heart transplantation will be our only choice. However, when Macbeth's heart, lady Macbeth, had huge problems – becoming a venomous scorpion, he never said: "My wife, you are wrong. We can't do such an evil thing." What he did was let his wife keep talking and keep brainwashing him, (Act 1, Scene 7, Lines 35-44). If you leave a sick heart in your body, it will let you die; just like if you leave a vicious wife beside you, she will lead you to your death.
The humanness of Macbeth was cruel but he still had some conscience which made him go crazy.