I sure hope you didn't pay too much for this. I use USPS all the time to send out plants and don't have this much trouble. In fact some here will give you much better plants for postage only.

Your pant is showing signs of major rotting. May be terminal. Keep away from other snake plants and if you have sulfur power, use a sprinkle on it. No more water till it shows signs of improvement. Some here use cinnamon. I have never had luck with this. Check on line for Sulfur power or big box stores sold for acid loving plants. If there are any mites hiding in there, try Listerine mouth wash or similar to spray the plant with.

Keep us informed on how it's going.

Thanks so much!

I'd return it to Vendor & ask for my money back. The plant is clearly quite damaged.

(I know Etsy as a site related to Art & Craft, don't know why one might buy plants there.)

Oh my goodness, that looks really bad. I can't believe a week in a box would cause that. It was probably already in poor condition. I would contact the seller and show them the picture. You could also make a complaint to etsy if you can't resolve it with the seller. Good luck!