I think it's a pressure effect that's both causing and being caused by the kidney disease, but that's linked to the hyperinsulin axis of type 2 diabetes, not really to the sugar.
The cholesterol meds can actually destroy the kidneys if they cause rhabdomyolysis - this is the primary reason I think using statins in CKD patients is triable as malpractice, and would vote guilty if I was a juror.
The "protein as bad for kidneys" thing is a half truth. High protein when you already have a low GFR can overload your body's ability to clear the urea (resulting in uremic disease), but a low carb diet (which you may be speaking about with the replacing carbs with proteins) is replacing carb (an energy nutrient) with fat (another energy nutrient), not with protein (which is a building block which can be catabolised to carbs for energy) - the protein should stay roughly the same, or go up a mite (if you were deficient before), not up drastically.
Keto will increase cholesterol in some people, and I have no reason to believe that that would be atherogenic, especially in context of the five alarm fire that is prediabetes and your kidneys being blown porous by high blood pressure.