I am 75 years old, and I have been constantly rehabbing minor hamstring pulls for the last 10 years. I recently added the snatch to my program (not every workout), and I have had no problems for the last nine months. Is this just a coincidence, or is it possible that the snatch is helping in ways that squats, deadlifts, lunges, etc. weren't?
First, let me say I think it is great that you incorporated an exercise like the snatch into your routine at 75 years young. People half your age fear the exercise! Without the chance to evaluate you nine months ago or even now, I will give you my best guesses for how the snatch has made a difference where the other movements did not.
One of the most common problems I see with my clients is what Dr. Stuart McGill calls “glute amnesia.” Essentially the glutes forget how or when to fire, and the hamstrings are forced to work double duty. This overload on the hamstrings can result in feeling continually tight and in having recurrent hamstring strains. Even the squat and other exercises may not awaken the glutes.
The squat and deadlift are excellent lower body exercises, but it is all about the firing patterns. Depending on your form in the above exercises, your glutes may have been able to still "hide" despite the weight used. A new and faster stimulus may have been needed to break the old patterns (glutes not firing and hamstrings working double time). A "quick lift" like the snatch fits the bill.
I would begin with the Gray Cook Hip Lift to evaluate the glute versus lumbar extension patterns. Basically begin on your back with one knee pulled to the chest and a tennis ball held between the ribs and thigh. The other knee is bent with the foot on the ground at mid-line (toes up, heel down). Now perform a bridge and do not lose the tennis ball (if you do, you used your lumbar spine to perform the extension and not your glutes). You can use your hands to give a small amount of assistance until you can lock in the tennis ball and use your glutes for true hip extension.
Back to the snatch. The snatch is a coordinated, quick hip extension and transfer of energy from the ground up through the hips and core, resulting in the bar being locked out overhead. This new and "aggressive" firing pattern was probably just what you needed to get the glutes firing. Specifically, the "second pull" or full hip extension of the snatch may have forced your glutes to turn on. Also, training speed is important for "cementing" strength gains into patterns we can use everyday.
Whether with a kettlebell, barbell or dumbbell, the snatch broke your hamstring dominate pattern and got your glutes firing.