What is the explanation of Ali ibn Abi Talib's saying, "By God, I am his brother, his guardian, his cousin, and his heir, and who is more entitled to him than me?" And why did he say he was the Prophet's heir, even though prophets do not leave an inheritance?

The aforementioned hadith (definition) narrated from Ali, may Allah be pleased with him, was transmitted by a number of hadith scholars, but it was judged to be munkar (rejected) due to the独-独-独tafarrud (being獨-独-独the sole narrator) of some of its narrators, such as Amr ibn Hammad, who was accused of rafd (rejectionism), and Simak, whose narration from Ikrimah was idhtirab (unsettled), and Asbat, who was described as having numerous errors.

And assuming its authenticity, the inheritance mentioned in it is interpreted as the inheritance of knowledge, not wealth. For Ali was the closest of people to the Prophet, peace and blessings be upon him, and the most attached to him, as affirmed by a number of scholars.