Why did the Republic use the Clone Army if they knew it was created by the Sith?
The creation of a Republic army was being opposed by a Senator. Because of her opposition, she was trying to be silenced by an assassin. That assassin was revealed to be working for the Seperatists - led by a fallen Jedi, who was building an army of droids to fight the Republic. A Clone Army is discovered and the assassin working for the Seperatists was revealed to be the host for the Clone Army. This army was ordered by a dead Jedi - without the authorization of the Jedi Council - and a Jedi was discovered to have erased the location of the Clone Army from the Jedi Archives.
Was it not obvious the Clone Army had direct ties to the Seperatists? If you're going to fight a war - why would you fight with an army that was sent to you by the enemy?