What is the reason for not believing in some matters of the unseen, such as the beginning of creation, angels, and the torment of the grave, despite believing in Allah Almighty?

Whoever does not believe in the creation of Adam, the heavens, the earth, the angels, and the torment of the grave, is not considered a Muslim by the consensus of scholars; because he denies matters known to be essential to the religion, and explicitly stated in the Qur’an and Sunnah (definition). Therefore, whoever is in such a state must renew his faith, and believe with certainty in everything that came from Allah and His Messenger, and submit to it, so that Allah may forgive him for what he has fallen into.