Why is the Hadith that mentions (the lowest in rank among the people of Paradise will have eighty thousand servants and seventy-two wives) weak, while the Hadith that describes (Tuba is a tree in Paradise, a journey of a hundred years, the clothes of the people of Paradise emerge from its calyxes) authentic, even though they share the same chain of narration in Sahih Ibn Hibban?

The process of authenticating and weakening narrations relies on ijtihad (independent reasoning). This is done by collecting the chains of narration for a hadith and comparing them to identify any defects. A weak narrator may occasionally be correct, and their hadith may be strengthened by corroborating narrations (mutaba'at) or supporting evidence (shawahid) from the texts of revelation. This is what hadith scholars call "hasan li ghayrihi" (good due to external factors). The two hadiths involving Darraj from Abu Al-Haytham were weakened due to Darraj's poor memory of hadiths narrated from Abu Al-Haytham, not due to a defect in his uprightness. Al-Albani's authentication of the hadith "Blessed is he" (Tuba) was based on supporting evidence that strengthened it and elevated it to the level of hasan.