For an analogy, look at individual households. Many of them have over a year of debt, aka over 100%. Getting a mortgage of 3 or 4 times one's yearly income isn't that hard.

Now, people will argue that, for many, the value of their house will be higher. That is true, but the same applies to governments. Infrastructure such as roads has value.

Traditionally, in many countries, the state also owned airports, water pipes, and electrical wiring that brought in money. That, I think, is where the real problem lies for some countries: they have sold the stuff that brings in money without bringing down their debt.