How tire pulling benefits running

I have been doing a lot of tire pulling of late based upon my belief that this was working my cardio a lot and working my legs hard for the type of tactical endurance that I need. Now what do we need to run fast? Overall muscular endurance, but in particular in the legs. We also need cardiovascular endurance and increased lung capacity. I don't really lift weights anymore. I will do some heavy compound movements such as deadlift, push press, etc. once in a while, but most of my resistance training comes in the form of kettlebells, push ups, pull ups, etc. What I have seen from this is a great increase in strength, virtually no injuries, and no joint issues of any kind. I went for a quick 3 mile run yesterday and for the first time in my history, my legs were not a problem. My legs have always been the first thing to give out on me, followed by my wind. This time the only real issue I had was a bizarre pain in my shoulder, which I think may have been a one time thing. When I consider the power applied by my legs in dragging a tire up a hill, this was obviously beneficial. If you're a believer in workout totals of weight moved, this makes sense. In crossfit and other systems it isn't always a matter of saying "I can squat 255 lbs." It may be more a matter of saying "I moved 3,455 lbs. this workout." Going by this philosophy, I am moving a tremendous amount of weight by dragging a tire 3 miles. It is hard to estimate the true poundage, as a 40 pound tire dragged one mile over pavement, produces many more pounds moved than a 40 pound tire dragged over loose gravel for the same distance.
Proponents of traditional workout methods may declare this can't work because you are going to overtrain, but if you are training for maximal endurance, strength, and power, and keeping your workouts under an hour, how is this possible?
Put simply, you are working hard in order to be able to work hard.

P.S. I have now fixed the comments system so you don't have to register with google. Thanks Bert.