I'm sure you consider yourself a clever person, ever consider that the situation was more complex than your one line comment? That maybe it's possible the German banks were so happy to see a country that suddenly had the backup system of the European Central Bank, i.e. a country full of customers they could lend to, that they flooded it with offers of loans? That Greeks, like the sub-prime borrowers of the USA, thought "Well, if everyone is saying the future looks bright, why not borrow money and pay it back with the promised future income?".
That, if I knew my friend was going to be irresponsible with money but their parent was going to bail them out, why shouldn't I lend them money with interest? Is that irresponsible of me? Do I deserve to get all my money back, instead of suffering some of the losses as well? (In this highly simplicized example, I = German banks, my friend = the Greek society, their parents = the ECB. Not saying all of Greek society was irresponsible, but in aggregate, it was a risky "investment")
A lot of the Greek bailout could be summarized as the German government bailing out German banks with EU taxpayers' money...
Here's a long article about what happened when Germany got flooded with money in the 1870s: https://www.nakedcapitalism.com/2015/02/michael-pettis-syriz... . It's longer than your one line, maybe you'd rather hold on to your more succint (and maybe more intelligent) summary...