I created this amazing NPC that is kind of the guide towards the true story line; he's an old Grung war leader, his entire army gets decimated by these big bat creatures, and he is forced to live alone in the wild, for years. He ends up leading the adventure and they later learn that his friend died in the war and he is seeking out revenge on the person who did it.
Anyway, he's a pretty powerful character and saved the players' lives, many different times. However, I decided that I would kind of back him off a bit from all the fighting; so that my players could get the XP and Upgrade. This was done by him going off to hunt, or him kind of fighting his own battle at the same time they were.
However, two sessions ago they were fighting some bandits; and to kind of make it more interesting and to give them the chance to kill the monsters... I had one of the bandits cut open his leg. This caused him to fall unconscious from the loss of blood (a more reasonable explanation for why my NPC wouldn't be able to help). This idea was amazing in my head, however I found out a session later that the players didn't think the same way.
I don't know if they have any idea of what I was trying to do, because they now want to leave him in the wilderness. They said that he is kind of useless and no help whatsoever. The problem I'm having is that my NPC was supposed to be this awesome character to give backstory and maybe some aid.
However, now that I tried to actually give my players XP, they want to leave him. I guess the question is not only what to do in this situation, because he kind of has a main part in the quest, but it's also how to prepare for the future.
In my future NPCs, what should I do different?