For Simba it wasn`t easy to realize that his dead uncle had a family, who now saw in him the murderer of the father and mate Scar was.
It seems like a nightmare for Simba, suddenly in Zira`s eyes he was a murderer like Scar.
But there was another hard step in front of him. It was clear that Zira wanted revenge, even in her cubs eyes Simba could read that. The lions who followed Scar and saw in him the rightful king were now a danger for Simba and the Pridelanders. He had to do anything and so Simba needed to exile all of Scar`s followers, before another war would start.
It was hard for him to exile even the little cubs, but it was more worse to cut them from their beloved mother.
The pridelanders contributed their new king. There was no chance for Zira and the other lionesses who shared her anger to fight. All what they could do was to leave the pridelands.