While thinking about debt in $ makes sense for individuals or businesses, it's a classic mistake to do that if you are talking about national economics. Instead of $, it works better if you think about debt in terms of % of GDP (gross domestic product). Of course, GDP changes each year; its never constant.
Greece's debt is now about 170% of its GDP, and rising. In 2009, when austerity measures were first imposed, it was 130%. Most of that change was not due to greater debt (it only increased by about 6% during that time), but was caused when its GDP shrank by about 20%. And why is GDP down? Largely because of the austerity measures Greece’s creditors forced it to impose.
Greece, as part of the Euro Zone, no longer has its own currency (which it could devalue), and it could not control interest rates from its banks. Lower interest rates could make for easy business loans and might create conditions for a growing GDP. The result was an economic implosion that ended up making the debt problem even worse. Greece’s formula for disaster, involved a toxic combination of austerity, without the ability to devalue its currency, and without the ability to lower interest rates.