It takes years to set up industries from scratch in competition with incumbents. How long does it take when you're the same company, have access to the people who know how to do it and can spend more resources than normal because low supply has resulted in high prices?

> And how willing would someone be in investing billions today that might be useful in 1-2 years but at the same time be aware that once china is full production they might not be able to compete for price/quality. Even the machines to manufacture stuff are mostly produced in china

It's events like this that cause reevaluation of supply chain diversity. Companies don't want this to happen again, so they keep the new facilities online even when the old ones come back to hedge against it happening again.