The clusters are headed along this path because the Universe is, or the local Universe we exist in is in, a jet.
The following is an image analogous of the Universal jet.
The reason for the 'expansion' of the universe is the continual emission of aether into the Universal jet. Three dimensional space associated with the Universe itself is not expanding. What we see in our telescopes is the matter associated with the Universe moving outward and away from the Universal jet emission point. In the image above, '1st Stars' is where aether condenses into matter.
Dark energy is aether emitted into the Universal jet.
It's not the Big Bang; it's the Big Ongoing.