Soon after Carlos Ghosn was taken into custody last fall, kicking off a bizarre legal odyssey that's transfixed the automotive world, some wondered whether the financial crimes he'd been accused of were serious enough to warrant the shocking arrest of Nissan Motor Co.'s fabled chairman.

Turns out that was just the opening act. The initial arrest last November — over what some viewed as a relatively minor charge of understating compensation — was a tactical move to buy time to analyze money flowing to and from Oman, according to people familiar with the matter. Additional charges followed. Nissan executives have since been cooperating with Tokyo prosecutors and received plea agreements in at least two instances, according to the people, who asked not to be named discussing private matters.

The ousted auto titan is now facing far more serious charges that he enriched himself via a web of complex financial transactions involving business partners in Oman and Saudi Arabia, as well as in his ancestral home of Lebanon, where he's still lionized as a visionary.