Why does the DMM make this circuit "work" ? (Power issues : servo & bluetooth)

BabyGeezer:
if the accumulation is unstructured and quite haphazard in its collection, it becomes quite inefficient and the knowledge is filled with (unknown) gaps.

Which is to be avoided where possible. And there are gaps in knowledge.... which is why pursuit of science knowledge and methods is ongoing. Science and engineering and other disciplines have gotten us to this interesting technological stage.... I have no issues with the 'structure' and 'efficiency' side of things with science.