the German (and French) banks are upto their eyeballs in Euro debt, including the original Greek debt. the bailouts have only been loans to cover repayments and interest for a short period, the debt is still largely outstanding, and the banks that hold them have massive problem if they have to write them off following a default. so, in effect, the bailout is proping up German banks. this is why its deemed just about acceptable. the big FU to the Germans is that the Greeks is saying "we want a deal on our terms, not yours, or up yours we're off", knowing full well they cant really afford to leave the Euro*, but neither can the Euro start having people leave as its the beginning of the end.
*Euro, not EU, i dont believe Syriza has ever been anti-EU.
But it stands to reason that most of the money came from France and Germany as they were the wealthiest at the time; the money had to come from somewhere. But other countries also contributed and are "being propped up as well" if this is the term you wish to use. It's not just the German banks.