Pretty sure all ram manufacturers are Korean?

Micron is American, headquartered in Boise, Idaho. Western Digital is based in San Jose, California. Kioxia (formerly a department of Toshiba) is Japanese.

Only Samsung and SK Hynix are Korean.

So, I don’t see anyone investing 10 years into the future to make ddr6 ram where their business plan relies on current trends.

Even if you're not up to DDR6, there's money to be made in lower-tier memory for lower quality devices. Also, when the market is in a pinch, you'll have the ability to scale up with investment dollars faster if you're already in the business.