I am not convinced that a gradual shift in Asian countries towards keeping their students at home can explain a 25% drop in one year. Are their underlying sudden changes in the economy, like the exchange rate, like recessions in the other countries, etc? 

We need to find a sudden change to explain the sudden drop-off. The article mentions the Trump travel ban, but without seeing the ban was only an expression of an underlying change in how the US is relating to the rest of the world and being perceived. Much of the world's population is concerned about Trump's election and what it says about American society, culture. I can see where foreign students, or their parents, might decide to make alternate plans while they wait to see what this all means.