Their high national debt is more of a consequence of their stalling economy than a result of it though - in the form of counter cyclical fiscal spending. In the 90s nobody wanted to spend so if the government didn't step in and act as a "spender of last resort" the economy would have imploded.

Either way it's not a cause of their economic problems, and the doom-mongering around too high a national debt leading to hyperinflation proved to be the exact opposite of the truth - they struggled with deflation.