Umar ibn al-Khattab was not the exception...
Umar ibn al-Khattab was not the exception, there were many companions holding similar views at Hudaybiya , demonstrating their reluctance, to the command of Rasool-Allah -saww , as reflected in their lack of response in commencing with the ritual of slaughtering the animals (as in Hajj rituals), and for that Rasool-Allah -saww had to ask them repeatedly, “Go and sacrifice and shave your heads.” Nobody heed to his -saww orders even when they were asked several times.
This was, just after a few hours from their pledge under the tree. The disobedience to Rasool-Allah -saww continued by some from the same group of Muslims as another striking example is when Rasool-Allah -saww asked them to join the army headed by Usama bin Zayd, to which they never joined, even after repeated requests from Rasool-Allah -saww .
After the passing away of Rasool-Allah -saww , some companions (who pleaded allegiance under the tree) continued to differ, resulting in their rejecting some of them, fighting of them in the battle fields, and dividing Muslim Nations in many sects due to their actions and changing of the Sunnah of Rasool-Allah -saww .
As we see the first caliph was selected under chaos and infights among a group of about 14 Muslims who met at Saqifa where Umar pledged allegiance to Abu Bakr, then Umar was nominated by the first one and then the third Caliph was an outcome of an arbitration among six nominees forwarded by the second caliph.
Hence, all companion of Rasool-Allah -saww , in general and those under the tree in particular, did not manage to carry through the praiseworthy title of ‘رَضِيَ اللَّهُ’ except for the few devout ones! May Allah -azwj Guide us and Keep us with those whom He -azwj was pleased with (‘رَضِيَ اللَّهُ’), Ameen suma Ameen.