There were several people within the Fuhrer bunker who decided to commit suicide before being arrested and tried by their war crimes that it is very reasonable Hitler was pretty much mentalized he would not be captured alive.
He had created a very high and inflated cult of personality in all captured Nazi Europe and he would have not survived the humiliation of getting caught by the enemy, when he asked his own generals and commanders to commit suicide instead allowing themselves to become war prisoners in the hands of the red army.

Hitler simply could not imagine a world without a victorious Germany and once that possibility was our of his reach, he decided to end it all. It is pretty simple.