Quite a few misconceptions here about the Renault-Nissan-Mitsubishi alliance.
From wikipedia: https://en.wikipedia.org/wiki/Renault%E ... i_Alliance
The strategic partnership between Renault, Nissan and Mitsubishi is not a merger or an acquisition. The three companies are joined together through a cross-sharing agreement.
The Alliance is a strategic partnership based on the rationale that, due to substantial cross-shareholding investments, each company acts in the financial interest of the other—while maintaining individual brand identities and independent corporate cultures. Renault currently has a 43.4 percent (fully voting) stake in Nissan and Nissan holds a 15 percent (non-voting) stake in Renault effectively giving Renault control.
The crux of the matter is this:
The Alliance began on 27 March 1999. At the time, the auto industry was in a period of rapid consolidation. Numerous companies merged or were acquired in high-profile deals, most notably Daimler's acquisition of Chrysler in 1998 (which dissolved in 2007, when the companies separated).
At the time it was created, Renault bought 36.8 percent of Nissan's outstanding stock and Nissan vowed to buy into Renault when it was financially able. In 2001, after the company's turnaround from near-bankruptcy, Nissan bought a 15 percent stake in Renault, which in turn increased its stake in Nissan to 44.4 percent.
Although Nissan is far larger and more profitable than Renault (and has a market value approximately double Renault's as of November 2018), Renault has effective control over the Alliance due to its significant voting stake in Nissan and its Nissan board seats (contrasted with Nissan's non-voting stake in Renault).
In addition, the single largest shareholder in Renault is the French government, which may have the effect of placing Nissan policy under French government control and has contributed to resentment over the terms of the Alliance within both Nissan and Japan.
I'm by no means qualified to comment on the intricacies of this corporate arrangement, but it seems the whole Ghosn case was an attempt by the Japanese to change the balance of power within the alliance.