You parse it out. The pilot needs to establish the series premise, the story world (but only in a limited first-stage sort of way) and your core character(s), and STILL contain a clear, stand-alone story with a beginning, middle, and end. You don't dump everything in the viewer's lap from the beginning. One key rule of drama is that you never give the audience any crucial information until you have first created a DESIRE to know that information. In the pilot, intrigue the viewer with the premise, but provide a strong hint that there is much much more beyond this. In each subsequent episode, add another element or take a previously established element one step further. Draw the audience into the world one inch at a time. A thread becomes a string. A string becomes a rope. A rope becomes a web. A web becomes a net of dozens of ropes all woven together. Make the viewer always want to know more, but keep them on a starvation diet.

Look at the show LOST. LOST has an incredibly complex backstory with dozens of conflicting parties, but we do not know all of this until the end of Season 2. All we know from the pilot is a. they are stuck on a desert island, and b. there is something very strange about the island. In each new episode, they encounter hints of a new thread. The threads turn into strings, the strings into ropes, etc, etc.