First, folks remember that y'all are cooking the meat with smoke. There is a difference between that and "cold smoking" like you would do for dry bacon or a dry cured ham, which is a process of several says at about 90 degrees.
There are some factors to tenderness when dealing with venison.
First, if the animal was chased, i.e. it was wounded, and you jumped it up when tracking, the adrenalin "dump" tends to make the meat tough. Second, the age of the animal; older tends to be tougher, so folks going for that once in a lifetime trophy rack should not expect good eatin' (imho). Third, diet. If the deer at any age have to roam far, and the forage isn't that good, then they will be lean and tough, but if they have lots of food, and don't need to go far to get it, they tend to have more fat, and be tender. Fourth, venison tends to be more tender when cooked rare.
To "fix" the lack of tenderness, you can..., age the meat, but this needs to be done under a controlled environment for it to actually work. Some folks who "age" their meat are really rolling the dice between actually having no effect, to spoiling the meat. The other answers may be found in how you prepare the meat.
You can break down the fibers in the muscle tissue with meat tenderizer, or some marinades, but that often does not help with a big roast, as they are often too thick.
Now many many decades ago, beef wasn't grain fed at any time before butchering. This was true in Europe even in the 20th century. So by our standards that beef would be tasty..., but tough..., due to the low amount of fat in the meat. This is what is going on with the venison for many of y'all, and what some folks are attempting to do when they add bacon or other fat to the outside of a roast..., adding fat. The problem is sometimes the meat is sooo lean the fat added just isn't enough, or the roast is so big, you really can't add fat from the outside. Brines injected to the interior of the roast, must contain something like a meat tenderizer such as
Papain or other ensyme to break down the meat fibers, or it must contain a fat or oil like olive oil, or it won't work.
So back in the day, to prepare a large, lean roast, even when it was to be served "rare" or "medium rare", they used a technique called
Larding. A specific cut of pork fat, that was resilient, was injedted into the roast to add the fat. Most of the fat came out during the roasting, but enough of it permeated the meat, and kept it moist and tender. Now this isn't rendered "lard", but is fat from near the skin, sometimes called "fatback" but without any meat.
So when all else fails, you might want to try larding, and you can find the tool here:
Lehman's Larding Needle
Try this. You may have to hunt around a bit for a butcher with the right type of fat to cut into strips, but this was a tried and true method for correcting dry, tough meat.
LD