I will say that in my painful experience, there is a difference between odors that are in or of the leather, and odors (such as smoke) that are on the leather. The latter can be eliminated; the former cannot.
A few years ago I had a Marc Jacobs leather jacket from NAS that I thought was stunning, but it had such an overwhelming moldy odor that I couldn't stand it. I kept the jacket, hoping against hope that I could get that odor out. I hung it outdoors on my porch in dry and breezy weather for days on end. I sealed it up in a ziploc bag with activated charcoal. I paid $45 to dry-clean it. I spritzed it with perfume, with Febreeze, with anti-bacterial Lysol spray. Finally, in desperation, I tossed it in the washing machine and gave it a bath. You can read about the whole adventure here.
Nothing helped one bit. I think mold had gotten into the "fiber" of the leather on one of its shipping journeys, and that it had been used in the manufacture of the Marc jackets anyway because some buyer got a deal on the price. Because it was stinky.
It does sound to me like what you're describing will also not be helped by anything you can do.
So sad, isn't it?