The murder was not as nationalistic as you may think. It was done by the Mufti, a bitter personal enemy of Abdallah, when the latter made a pilgrimage to the al-Aqsa Mosque, the jewel in the Mufti's crown. The Palestinian state would have been ruled by the Mufti, but he was denied that when the King took Jerusalem and the West Bank (the term of course stems from the Jordanian years). The Mufti was not a man to be crossed lightly and he took his revenge.
Anyway, the Palestinians bear as much of the blame for not having a state in '48 as anyone.