What did Ibn Abbas mean by his statement: "As for him, He sent him down as a father," and what is the relation of this phrase to the aforementioned Hadith?

Ibn Abbas and Ibn Az-Zubayr, may Allah be pleased with them, ruled that the grandfather is in the position of the father in inheritance, thus excluding the siblings, citing the statement of Abu Bakr As-Siddiq, may Allah be pleased with him. Scholars have unanimously agreed that the grandfather does not inherit if the father is alive. Ibn Abbas chose Abu Bakr's opinion, which considers the grandfather as a father, thereby excluding all brothers and sisters from all sides, attesting to Abu Bakr's virtue and his standing with the Prophet, peace and blessings be upon him. According to this view, full or paternal siblings are excluded by the grandfather, just as they are excluded by the father. This is the opinion of Abu Bakr As-Siddiq, Abu Musa, Ibn Abbas, and fourteen of the Companions.