While Germany believes that Grexit is manageable, Grexit gets ever more likely, because what reason is there for Germany to compromise?

"Manageable" is not the same as "better than any alternative". The incentive can be that, while it may be manageable, a better situation could ensue without it.
For different definition of better, depending on what they care about. For some, it could mean how history will judge them. Regrettably, Schauble is too old to care as much about his future as we would like and seems intent on leaving the wrong kind of trail. But maybe others will see things differently.

Anyway, I am not saying you are wrong necessarily, just that it may not be as direct a conclusion as it seems.

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi