I don't think anybody is trying to exalt the Garand to "war winning" status all by itself.
I read somewhere that the vital inventions/equipment in WWII was the Jeep, the C-47 cargo plane, the P-51, the M1 Garand, and radar.
Ultra and the work at Betchley Park is probably the big one, as far as the ETO.
In the book "Dirty Little Secrets of WWII", the author points out that years after the war (late 1950s or 1960s, can't remember) a panel of German politicians were told about Ultra and the degree to which Germany's wartime codes and decisions were penetrated.
Even after that passage of time, the politicians were shocked and bewildered. They had no idea.
Stephen Ambrose wrote that the Germans did not particularly fear our infantrymen. Or our tanks. What they absolutely could not STAND was American artillery.
It was numerous. It was accurate. It possessed many specialized shells of high quality and very low dud rate. Any 2LT with a radio could bring down a torrent of accurate, deadly fire in minutes with little difficulty.
Once you've got your sights adjusted to the ammunition you have, step away from the bench. In competition or the field...there are no benches.