I’ve understood that electrons move in a 3D field outside the nucleus and that they are quite far away from the nucleus itself (in relation to the atom scale).
What would happen if you pushed them out of this moving field of theirs, closer to the nucleus?
You get neutronium. Basically, what happens is that as you squeeze the electron closer to the nucleus (with gravity, for example) the electrons can combine with the protons (and an antineutrino) to make more neutrons. This is what happens when neutron stars form (and why I used gravity as the example force)