Indeed, Asta becomes the Wizard King. His journey is filled with hard work, friendship, and facing powerful adversaries that all lead to this ultimate achievement.
Scar's path to becoming king is full of treachery. He first plots against Mufasa out of jealousy. He makes a deal with the hyenas to help him carry out his plan. During the wildebeest stampede, instead of helping Mufasa, he takes the opportunity to murder him. He then lies to the pride about what happened, making Simba believe he was responsible for his father's death. This way, Simba runs away and Scar takes the throne. His actions are driven by his desire for power and his envy of Mufasa's position.