A little background: The precursors created the humans and forrunners. The forrunners ended up killing all of the precursors except for 1. (Lots of missing details, too much to explain) That sole surviving precursor ended up nearly wiping out the entire forrunner race out of revenge. Single handedly, the last precursor killed 100 billion plus people alone. The precursors pretty much had control over the very existence of every conceivable thing. Their collected knowlege dates back 6 billion years, abd their power alone would be more than enough to dominate the star wars universe. Source: the halo forrunner saga books