In contemplating the "drivers" and "direction" of evolution the very terminology invites a consideration of some kind of divine power.....But.
In the analogy of a stream of water making its way down a mountain, it's the places the water doesn't flow which imply the direction of flow. So the banks at the water's edge block any flow up hill and the remainder makes its way downwards drawn by gravity. This appears to create a sense of purpose to the flow of a trickle which becomes a stream and then a river. That mighty river however is only what is left over after all the places the water didn't flow!
In evolution the subtle fragility of DNA allows for a drift in genetic message generation by generation. The desirability or otherwise of these changes makes evolution happen. Less advantageous changes make for non survivors. Those surviving "fittest" are just the leftovers who haven't been deleted by the rigours of life in the jungle.
The flow of water down the hill has no purpose to its direction of flow. It just happen upon a course drawn by gravity where its flow isn't blocked.
Evolution just happens upon its merry way facilitated by the fact that DNA copies with slight transcription errors generation by generation. This slow inexorable change is the "gravity" driving the direction of evolution.