Einstein will be vindicated, since the key to understand entanglement lies in the theory of Special Relativity.
As you correctly state, Einstein objected to Quantum Physics by the principles of realism and locality.
The problem is that Einstein didn't quite grasp how his own theory redefines those two terms.
First, we should stop thinking of massless quanta and field disturbances as entities or processes that propagate at the speed of light through spacetime. Massless quanta and field perturbations, by tracing null geodesics in spacetime, are more like instant connections between the emission and detection coordinates when they comply with the light speed ratio. So the objective reality of any massless entity or process that appears at the speed of light to us is that no time elapses for itself, regardless of the subjective spacetime interval we experience from our reference frame. The true nature of any phenomenon that manifest as traveling at the speed of light to us is the instant bridge it represents through spacetime. Any photon, gluon or field disturbance we picture as propagating at c is, also, the entire emission-flight-detection process, somehow. Any distance, duration or sequence of events we think they covered, lasted or endured gets compressed to a single point and instant of simultaneous, timeless existence for them. So a massless quantum represents more of an entanglement between emitter and absorber than a particle traveling between them, and the speed of light is the incredibly distorted way in which its instantaneity gets mapped in the subjective reference frame of the observer.
Looking at fundamental interactions from this perspective, now every energy or information exchange can also be seen as an instant action/reaction event without spacetime qualities. So if an event that happened 13 billion years ago can affect a detector here and now, then what does "locality" even mean? The definition of locality should be "expanded", as every piece of matter is affected not only by its immediate surroundings, but by every fundamental interaction that reaches it at the speed of light, regardless of how past or far away the event to which it connects through spacetime.
Second, we should stop thinking that matter, forces and spacetime are composed of different entities. Any phenomenon physically existing is, in the end, just a pattern of fields, or a network of fundamental interactions. So there are no different elements with different intrinsic properties composing each aspect of reality. Every energy or information exchange, any piece of matter, any property, structure, sequence, entity or process that physically exists in the universe is ultimately made up of the instant but light-like interactions that shape their internal structures, and those that communicate them. The fundamental interactions that unfold each time compose every phenomena that exist, and interconnect the actual configuration of space with all its past history instantaneously, stitching reality in a consistent way by virtue of the speed of light constraint.
Looking to physical phenomena this way, now every property, entity or process can be seen as a pattern that the different fundamental interactions compose "on the fly" each time. Every light-like interaction that emerges is, in fact, instantaneous and complete the moment it unfolds to reality, so the definition of realism should be "contracted" to exclude any explanatory mechanism that changes or evolves in time, since properties are not really "carried" by material particles, or "propagated" through space by massless quanta. The whole universe is recreated before our eyes each and every time, just by the fundamental interactions that instantly connect the present to the past in a self-consistent way through the speed of light relation.
In this regard, Einstein with his predefined hidden variables, and Quantum Mechanics with its probability superpositions, collapses and branching many worlds are both wrong about the tools they use to explain reality, since no spacetime concept that changes or evolves in time can properly describe the instant nature of the universe. Nothing "evolves" through spacetime. Not even matter. Each interaction has to meet some conditions and constraints in order to emerge, but what emerges (if it does) is a collapsed wave function already, complying at once with all the requirements for the emission-flight-detection process we imagine it endured in sequence. But the truth is that before the moment an interaction finally emerges to reality, it doesn't exist at all.
Local hidden variables have been proven wrong, but even wave functions and branching worlds are only convoluted ways of describing phenomena that appear as processes unfolding at the speed of light to us, but are instantaneous by what the speed of light implies, so our "spooky action at a distance" is "action at spooky distance" to them.
As said earlier, every energy or information exchange we usually picture as a process can now be seen as an instant action/reaction event enforcing a conservation law. So all the massless carriers we picture as travelling the universe at the speed of light are, at the same time, the instant entangled connections that create the spacetime structure itself, the information exchanges that hold up reality.
Entanglement is the fundamental principle that drives the universe. It is not something that develops only under some specific conditions, since it underlies all physical phenomena in the universe, but it is hard to evidence.
The duality of the speed of light as instantaneity explains entanglement, and from there, all quantum conundrums can get solved.
