On one level, last week was the most shocking of the Trump presidency: The government shut down in a fight over a border wall, the president started the process of pulling troops out of both Syria and Afghanistan, the defense secretary quit and the stock market plunged amid great uncertainty.

On another level, it was the most predictable week of the Trump term. Every explosive event was forecast when Mr. Trump ran for office, and was more or less inevitable once he became president.

It...