This was partly because real interest rates were very low (and, indeed, often negative) throughout the decade. This situation could not last forever, and it did not. Once real interest rates returned to higher levels and the economy continued to experience lower trend growth rates, the vicious circle of debt dynamics set in.
Overall, one can view the period since 1970 as one in which the authorities struggled to establish appropriate medium-term anchors for both monetary and fiscal policies. During this time, they learned about the appropriate interaction between those two policies in the context of economic stabilization and growth under a flexible exchange rate regime.