When creating a "thought experiment" a main problem is to set up conditions that describe a realistic setup. The so called "Capacitor Paradox" https://physics.stackexchange.com/questions/437409/paradox-involving-two-capacitors only comes up because the connection is set to have no inductance. 

So what is the setup of the double slit experiment with electrons: The incoming electron's kinetic energy is about 50 keV. The slit's width about 0.5 µm, the distance 2 µm. The original paper: https://www.leifiphysik.de/quantenphysik/quantenobjekt-elektron/geschichte/originalarbeit-von-joensson  shows relations and difficulties.

As it is extremely hard to get the pattern it is extremely simple to destroy it. But that doesnt explain, why the pattern exists.

As Jönsson wrote: there has to be a slot (in optic a grating on a transparent will work) as no material object is not covered with electrons, and indeed: the incoming electrons only see a sea of electrons and two areas with no electrons. In the classical world every electron will just pass through a single slot (if not reflected)  and we will not see interference.

In the quantum world interaction between two electrons is quantized. And now we can see two cases: 

The incoming electron interacts with a single electron in the sea and passes the slot. It will appear at a distinct place. The position of the sea electron is influenced by all the surrounding electrons so the geometry of the slits will be reflected in the average target points on the detector screen. So what we see is the interference between two electrons following the rules of quantum mechanics. Then many of the electrons will in average show the interference pattern. 

The second case is: we see the sea of electrons as a condensed unit that results in one single, complex wave function and the interference of the incoming electron with this wave function creates the pattern.

However: there is a fundamental difference between a macroscopic interference (where a wave is just a analog wave) and microscopic interference (where a wave is constructed from elementary wave particles). And we should not forget that the double slit experiment only is surprising when not related to quantized interaction between particles. Only the integrating property of the screen makes a pattern from events. It's not at all a great idea to do statistics from single events.