> Trump had been threatening tariffs

Trump made many empty threats his first term, so many didn't believe he would follow through to the degree he's done this term.

> The EMH would assert that a casual observer like me wouldn't see the price gap between the time it took for people to read sentence 2. But it took several business days.

This is a good point and surely sounds like an effect of liquidity demand. The same investors had to dump Nvidia also to pay for other losses and that briefly removed liquidity providers who wanted none or the volatility, until things calmed down a little.