They played first, learned how to hit the ball by observation and imitation and repetition. Of course, this process is antithetical to the way all top golfers learned to play the game. I do not denigrate all the analysis. If you peruse these books and videos you will quickly realize there are infinite variations to the good golf swing. Now here's the rub.
Instructional books are generic.
They are written for a mass audience, and therefore set forth a general set of movements for the swing. At the top of the back swing the club should point to the target. On the downswing the path should be inside, then strike the ball, then to the inside on the follow through. Follow up with raising your right foot. Along the way there are certain positions for your head, your elbows, the ball on the ground, your feet and your hands on the club.