I hope that this diagram is large enough to understand. Two ropes. Two bags. No rope is tied off to a tree or hanging down within reach.
This is the system that we used in Yosemite from 1978 until about 1999, when bear canister rules starting to come around. Based on the size of the trees, the size of the branches, the size of the bears, etc., I found the best length of rope to use for the A rope was about 60 feet. The B rope could be shorter, like 40 feet.
The extra length is what keeps you from having to pull the weight _down_. By getting out at an angle, you pull the weight out. That takes slightly less effort which is important with heavy loads.
I can still remember watching three guys trying to hoist-away on an army duffle bag that was filled with over 70 pounds of group food. First of all, a duffle bag hangs down so far that you have to have a very high branch. It takes a tremendous amount of effort.