God's mistakes are numerous, but a short list would include overestimating himself, creating a planet/environment unsuited for its inhabitants, creating a species he loves and adores but hates enough to doom them all to eternal torment and commit genocide against them more than once, and managing to fuck up almost everything despite being omniscient AND omnipotent.
Exactly. Religion is a brilliant tool for control.
Order is pretty much the only benefit that comes from it. Even then, too much of a good thing can be quite counterproductive.