In the Copenhagen Interpretation wave functions are supposed to represent probability distributions of collections of electrons viewed as "particles in void" in the same way as the Greek atomists did 2500 years ago.
The contribution from modern physics to this ancient view is the element of probability eliminating causality by stating that "particles" are supposed to "jump around", or "jiggle" in the terminology of Feynman, without cause and thus always be nowhere and everywhere in the void at the same time.
Schrödinger compares this ancient "particle" view boosted by probability with his own opposite view that "all is waves without void obeying causality" as possibly a true advancement of physics. This is the starting point of realQM...as ontic/realistic/objective rather epistemic/idealistic/subjective...
Recall Roger Penrose in Foreword to Nature and the Greeks and Science and Humanism:
- Moreover, in my personal view, the more "objective" philosophical standpoints of Schrõdinger and Einstein with respect to quantum mechanics, are immeasurably superior to "subjective" ones of Heisenberg and Bohr.
- While it is often held that the remarkable successes of quantum physics have led us to doubt the very existence of an "objective reality" at the quantum level of molecules, atoms and their constituent particles, the extraordinary precision of the quantum formalism - which means, essentially, of the Schrõdinger equation - signals to us that there must indeed be a "reality" at the quantum level, albeit an unfamiliar one, in order that there can be a "something" so accurately described by that very formalism.