Why did Hajj precede fasting in Ibn Omar's Hadith (Kitab al-Arba'in al-Nawawiyya)?

SUMMARY:

The precedence of Hajj over fasting in the Hadith "Islam is built upon five" is narrated by Al-Bukhari. Muslim also narrated it in four versions from Ibn Umar, two of which give precedence to the fast of Ramadan over Hajj, and two that give precedence to Hajj. Al-Hafiz Ibn Hajar chose the opinion that the reason for Hajj preceding fasting stems from narration by meaning, and that the original order gives precedence to the fast of Ramadan, evidenced by Ibn Umar's correction of the man who gave precedence to Hajj over the fast of Ramadan, saying: "No; the fast of Ramadan and Hajj. This is how I heard it from the Messenger of Allah, may Allah's prayers and peace be upon him."