Simplify the following text for a Grade 16 native English-speaking person.
Original: His son became the next Inca without any known dispute after Pachacuti died in 1471 due to a terminal illness , but in future generations , the next Inca had to gain control of the empire by winning enough support from the apos , priesthood , and military to win a civil war or intimidate anyone else from trying to wrest control of the empire .
Simplified: His son became the next Inca without any known dispute , but in future generations the next Inca had to gain control of the empire by winning enough support from the apos , priesthood , and military to either win a civil war or intimidate anyone else from trying to get control of the empire .