Kent states it correctly, The strap in the bilge is just to tie the keel to the bonding system. The keel, being iron is higher on the galvanic scale than the anodes and is bonded just like any other metal item on the boat that is immersed in salt water for it's protection. All the wires coming together from the various objects at the head of this strap merely acts as a central junction point so all the wires won't have to run all the way to the rudder post to which the sacrificial anodes are affixed (weight & cost savings).
I was confused by this for some time so I can understand.
