its all been said here im just gonna but it in my own words. The Droids lost on two fronts. The clones even though there numbers were low are better soldiers. They have insticts and feelings. They also in a phitness perspective have much more flexibility. But also they were under control of the emperor so thats how the CIS lost. Its seen in the Revenge of the Sith.
At last we will reveal ourselves to the Jedi. At last we will have revenge.