The "stability" is referring to how Trump's trade policies are constantly changing every few days, and are thus too unstable to plan business policy around. If Trump wants to promote US manufacturing, it's important that his policies to do so are stable enough for investors to plan profitable future US factories.
It is not talking about a stable government and the benefits/drawbacks of that.
The point is that if the trade policies are unstable, manufacturers will minimize imports and shipping across their supply chain. This isn't difficult to comprehend.
It is not talking about a stable government and the benefits/drawbacks of that.