Embattled auto industry executive Carlos Ghosn had amassed so much power that he was able to hamstring Nissan Motor Co.’s legal and compliance departments, preventing effective in-house oversight and allowing him to hide alleged financial misdeeds for years, according to a new report from the Japanese carmaker.

Nissan’s seven-member special committee for improving governance found that a “personality cult” had developed at the company, where “Mr. Ghosn was in a way deified within Nissan as a savior who had redeemed Nissan from collapse, and his activities were deemed impenetrable territory within the company.”