Think about your own post.
Did Japan stop at the Chinese mainland during their expansionist period?
Lol.
Japan was about Manchuria.
Japan has no oil. No coal to speak of. No nat gas. Northeast China, at that time Manchuria, now including North Korea, has oil and coal. So what did China have that Japan wanted or needed? Precisely that.
The attack on Pearl was because at that time the US was the Saudi Arabia of the world, exporting California oil elsewhere. Then FDR cut it off from Japan.
The only other source of oil Japan could access would be Indonesia and the US Pacific Fleet would obstruct that, as would US bases on the various islands of the Pacific.
It’s all about what another country wants or needs. And it’s ALWAYS about oil. China’s DaQuing oil fields will go empty, like California and Illinois and indeed, Oklahoma. They are grabbing hard for offshore locales with potential.
It’s all about what somewhere needs.