Short term trades can go up or down within a range bound by fundamentals. The further things get from their ‘correct’ value the more obvious the correlation becomes.
Aka, when people change their vacation plans etc based on currency fluctuations that’s a massive effect in aggregate.
Currencies trade confidence, not fundamentals, and if confidence in a currency disappears to the point where it stops being the default choice for transactions, the effects are almost literally incalculable.