You've no doubt removed alot of links that might have been helping you rank as well as did before. That may very well be why you haven't regained much of that traffic.
Another reason might be, the site is still under an algo filter like Penguin. The links you removed may have been enough for the manual reviewer, but not enough for Penguin. Or maybe it's enough for Penguin, but since it hasn't been refreshed since October ..you can't recover yet.