1) Why do we care about Ray Winstone's character, and why did Indy remain his chum after his treacherous behaviour?
2) If Oxley took the head from the skeleton in the first place, why does replacing it make the spaceship fly away?
3) What was the purpose of the kung-fu monkey people in the graveyard?
4) What was the point of the quicksand scene?
I'll take a go at these.
1) I suppose for the same reason he expressed a bit of sorrow when Sotipo died after betraying him in Raiders, or when he tried to save the life of the Chief Guard he was fighting on the rock crusher in Temple of Doom, or when he tried to save the life of Ilsa after she betrayed him and his father in Crusade. He?s not a heartless bastard even with those peaople who made bad decisions.
2) Oxley didn?t take the head from the spaceship; Francisco de Orellana the conquistador took the Skull, perhaps from Mayan natives. As for why the ship flew away, it may have had to do with the request of the one who returned the skull. Or maybe the alien was just pissed for having its head removed for so long that it decided to leave.
3) I thought that they were locals trying to kill grave robbers or from ancient tribes trying to protect their shit, and the fighting style was Capoeira which was developed in South America between the 16th and 19th centuries.
4) To put Marion and Jones in a confession situation. Apparently, if Marion hadn?t told Indy in all these years that he had a son, she wasn?t likely to tell him at all unless she was in a situation where she might be about to die.