Explain the theoretical foundations of Bell's Theorem and how it demonstrates the non-local nature of quantum mechanics. Compare and contrast the Copenhagen interpretation, the Many-Worlds interpretation, and the De Broglie-Bohm (pilot wave) theory in their handling of entanglement. Discuss how these interpretations differ in their view of wavefunction collapse and the existence of hidden variables. Ensure the explanation focuses on the mathematical logic and philosophical implications rather than experimental setups.