Bubbles last until they feel like fundamentals, and until last week, investors believed that tech stocks could only head up and the Japanese yen could only head down. By Monday's market opening, investors cowered for shelter as the two bubbles popped in unison.

The Biden administration in Washington and the Kishida government in Tokyo both pursued the same unsustainable policy, ballooning the government balance sheet to push up asset prices.

By July 31, when the Bank of Japan raised its short-term interest rate to 0.25% from zero and announced that it would "taper" its purchases of government bonds, the central bank owned half the outstanding float of Japanese government bonds.

Japan's debt-buying binge pushed up inflation expectations, weakened the yen and buoyed Japan's stock market during the past three years.