You may well have a bad turbo, and you certainly let your oil get low, but I don't necessarily think one caused the other.

Before I was attuned to the oil-consuming habits of my 300SD, I let it get way too low. How low? Low enough to make the gauge wobble down to 2 bar when changing lanes (slosh!) How low is that? 3.5 quarts below the full mark.

My turbo makes 12 psi, quietly, anytime I want. If I couldn't kill the turbo, I'm skeptical that you did.

I keep her full of Rotella with a check up at each refueling now. That was last year...