Certain countries started to demand part of their payment in gold, and the US gov was unable to do so, having long since embezzled and sold off all the gold in Fort Knox for private profit. (No auditioning of the gold has been allowed since the 50s. Gee, I wonder why!)

Making tungsten bars was just a desperate attempt to win a little time. They didn't gold-plate those tungsten bars thinking the Chinese would be fooled forever, they were simply trying to cover their asses for a couple more months.

These guys make up this shit as they go.