User blog comment:Miskos3/Chapter 56, Review/@comment-17563801-20140409195724/@comment-179280-20140410223229

Mind you, Flegel did not do anything wrong, and even doing something stupid as taking a piss saved his life. You know, the MPs killed Dimo and all of his men except for Flegel, so ironically, his "fickle" son will probably save the plan from failing.

I don't think him being childish means everything will go to waste. In fact, Levi's experience is what actually ruined the plan, since it caused Ackerman's men to inspect Eren and Historia and take the blades they were hiding in their bodies.