No, quantum entanglement does not prove the existence of absolute simultaneity and it does not contradict Einstein's theory of relativity.
Einstein's theory of relativity, specifically the theory of special relativity, introduced the concept that the laws of physics should be the same for all observers in uniform motion relative to each other. It also showed that there is no absolute simultaneity, meaning that the concept of events happening simultaneously in different locations can vary depending on the observer's reference frame.
Quantum entanglement, on the other hand, is a phenomenon within the framework of quantum mechanics, which is consistent with and does not violate the principles of relativity. When two particles are entangled, the measurements on their properties can be correlated, and the state of one particle can instantaneously affect the state of the other, regardless of the distance between them. However, this instantaneous correlation or action at a distance does not violate relativity because it cannot be used to transmit information faster than the speed of light. The correlation between entangled particles cannot be used to communicate or transfer information, and any practical use of entanglement is limited by the constraints of relativistic causality.
In summary, quantum entanglement does not establish absolute simultaneity or contradict Einstein's theory of relativity. It is a phenomenon within quantum mechanics that is consistent with relativistic principles, and its effects do not violate the limits on information transmission imposed by the theory of special relativity.