TOKYO — It was 2011, and Carlos Ghosn was preparing his automotive empire for its most ambitious phase yet. Under his plan, within five years, one of every 12 cars sold around the world would be made by Nissan of Japan . To achieve that goal and cut costs relentlessly, he said, Nissan would have to work closely with Renault, the French automaker he also controlled.

Some people at Nissan suspected another motive. Engineers at Nissan and Renault began receiving less money to develop separate models. In effect, they were being forced to work together. Nissan insiders worried that Mr. Ghosn was quietly trying to fuse the Japanese company to the French one.

But few dared to object or raise doubts about a possible merger. Mr. Ghosn was, as a critical governance report revealed this week, “deified within Nissan,” a leader whose decisions and activities were “deemed impenetrable territory within the company.” He was known to drive out managers who disagreed with him. He shared authority — and his plans — with only a few loyal executives.

Today, Mr. Ghosn faces charges of financial wrongdoing after being forced out of the company , and the tensions inside Nissan and across the alliance have blown wide open.