Japanese makes used to dominate the global market but in the last 5 or so years Chinese exports have gone from about 1 million to nearly 6 million annually. I think that Japanese makers are probably terrified and this merger is a defensive move against potential future contraction in their global sales. (I know this was not the point for the thread - sorry - just something I’ve been thinking about.)
(Sorry this article is behind a paywall - the gist is that China now significantly undersells much of the global competition through a combination cheaper labor, subsidies and late-mover advantages from having newer factories as a result of having just entered the market.
https://www.nytimes.com/interactive/2024/11/29/business/china-cars-sales-exports.html)