The book contends that Emperor Go-Toba lost the Jōkyū War because of his immorality, casting him as a villain, and that the event therefore does not necessarily challenge the authority of the emperor and his court.
The book suggests that Emperor Go-Toba's failure in the Jōkyū War stemmed from his immorality, branding him as a villain, and hence, it doesn't inherently question the authority of the emperor and his court.