After reaching the edge of the universe (if there is an edge), it would then take a long, long time for the thinly spread-out hydrogen and helium fog to devise a way to lock together (if the gas had the brains to figure out such a pressing problem).
So there is just not enough time in the evolutionary timetable from the Big Bang till the universe was filled with stars. The Big Bang theorists are divided on when it occurred; some say 20 billion years ago, others 10 billion. We will here assume the longest timeframe: 20 billion years. But quasars have now been found which, by Big Bang-accommodating theories, are "15 billion years old." This does not provide enough time for the gas to spread outward throughout the universe, form itself into stars, then wait while billions of supernovas repeatedly explode (to produce heavy elements [if they could do so]), reform into stars, explode more times, and finally form into our present orbiting stars, galaxies, clusters, and superclusters.
Before concluding this section, we will try to tack down the Big Bang dates. Generally, the Big Bang itself is supposed to have exploded 10 to 20 billion years ago, with the first formation of stars occurring 250 million years after the explosion. At some lengthy time after the gas coalesced into "first generation " stars, most of them exploded, and then, 250 million years later, reformed into "second generation" stars. Our sun is thought to be at least a second generation star, having previously exploded at least once, and perhaps twice. Apparently, no one ever dates the Big Bang earlier than 20 billion years ago. Here are several representative statements: