I would like a realistic evolutionary path for non-hominid humanoids, but evolution is extremely complex and varied, so I will narrow the question to examining how evolution might occur in felines to produce a humanoid. I would like to start with the Pseudaelurus (a prehistoric cat) and move to an upright walking, fingered and toed omnivore (cat's are obligate, "true", carnivores). I think I have a reasonable idea for how to evolve their diet (included below for reference), but I'm stuck trying to come up with a reason for hominid like fingers and toes and upright walking. My question is, what types of environmental/cultural/etc... changes could lead to a feline developing upright walking and hands capable of hominid like grasping?
Evolution of Diet: Assuming the cats were native to a plains environment with ample hunting opportunities, an environmental shift (ocean's rising, tectonics, something else) could force the felines into a wooded environment with a much smaller number of prey. This would lead to adaptations for including fruits and other forest products into their diets. It would most likely also favor tree climbing adaptations like those seen in leopards.