How does special relativity explain why simultaneity depends on an observer’s frame of reference?

In the philosophy of physics, the special theory of relativity explains that simultaneity is relative because the speed of light is constant for all inertial observers.12

To maintain this constant velocity, Albert Einstein demonstrated that space and time cannot be absolute. Because light takes time to travel, observers in different states of motion perceive the timing of events differently. For example, if two lightning strikes occur at different locations, an observer moving relative to those locations will perceive the light from the events at different times compared to a stationary observer, leading to a disagreement on whether the events were simultaneous.12

Consequently, there is no perspective-independent "present". Instead, simultaneity depends on the observer's frame of reference, as defined by the Lorentz transformations. This reveals that space and time are not separate entities but parts of a single, four-dimensional structure known as space-time.132