Decided to research a little more. Apparently Einstein was a thick cnut.

"Bell's theorem is a "no-go theorem", meaning a theorem of inequality that addressed the concerns of the EPR paradox of Einstein Podolsky and Rosen concerning the incompleteness of Quantum Mechanics. EPR stated that superposition of the quantum mechanical Schrödinger equation would result in entanglement, making it incomplete. John Stewart Bell was intrigued by this argument and created his inequality to disprove Von Neumann's proof that a hidden-variable theory could not exist. However, he discovered something new by rephrasing the problem as to whether Quantum Mechanics was correct and non-local (showed Entanglement), or whether Quantum Mechanics was incorrect because Entanglement did not exist. Contrary to popular opinion, Bell did not prove hidden variable theories could not exist, but he proved they had to have certain constraints upon them, especially that Entanglement was necessary.[1][2] These non-local hidden variable theories are at variance with The Copenhagen Interpretation in which Bohr famously stated, “There is no Quantum World.”[3] In the latter, the measurement instrument is differentiated from the quantum effects being observed. This has been called The Measurement problem and the Observer effect problem.

In its simplest form, Bell's theorem rules out local hidden variables as a viable explanation of quantum mechanics[4] (though it still leaves the door open for non-local hidden variables, such as De Broglie–Bohm theory, Many Worlds Theory, Ghirardi–Rimini–Weber theory, etc.).

Bell concluded: “In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements, without changing the statistical predictions, there must be a mechanism whereby the setting of one measuring device can influence the reading of another instrument, however remote. Moreover, the signal involved must propagate instantaneously, so that such a theory could not be Lorentz invariant.”[5]"

https://en.wikipedia.org/wiki/Bell%27s_theorem