...if we take the big bang as truth, is it not given that all four force were unified in the "beginning"...
You can imagine all the forces as the result of
curvature of surface curvatures of small droplets of matter, forming our vacuum and particles of observable matter, recursively. The curvature effect is given 1) by the tendency of energy to focus along density gradients and 2) the tendency of surface energy waves to spread along as straight path, as possible due the diffusion character of mass/energy concentration leveling.
But the effect of surface tension is ambiguous, which can be observed on small mercury droplets easily: the small droplets repel itself mutually at low distances, whereas they have tendency to agglomerate itself into bigger one. By such way, the tiny droplets can form the bigger one, where the repulsive and attractive forces are in mutually equilibrium. The elementary particles or atom nuclei can serve as an example of such hierarchical systems.

By
Aether Wave theory (AWT) these droplets have appeared as a result of condensation of hot false vacuum, formed probably by the interior of black hole, existing in previous generation of Universe. Such process is analogous to condensation of hot vapor into droplets, which are forming the gas, which condenses into droplets, which are forming the gas.... It's evident, if you heat such mixture, the droplets will gradually evaporate again, which will lead into disappearance of electromagnetic interaction, strong nuclear interaction and weak nuclear force, consecutively. Just the gravity will remain. This is explanation of GUT mechanism without using of big words, just by using of physical analogy.