don’t forget that the Garand itself was a fairly groundbreaking design as one of the first widely adopted semiautomatic battle rifles

Automatic weapons weren’t new. Every squad had an automatic rifleman, and submachine-guns were used widely. The question was whether it was worth equipping every rifleman with an automatic weapon. This wasn’t obvious at the time.

The M1 and M14 had superior range and stopping power. Being able to reliably kill the enemy and not end up outranged are intuitively important. Semi-automatic weapons also mean you don’t have your entire army burning through ammunition. When you’re fighting expeditionary wars, this is a major concern because every bullet has to get shipped halfway around the world.

No, it wasn't.

Automatic weapons were coming on line at pretty much the same time armies were going with fully rifles barrel breach loaders.

The Gatling gun is only not a machinegun by virtue of whacky legal definitions, and was around when most militaries had just upgraded their muzzle loaders. WW 1 was the era of the belt fed machinegun. Take a crew served belt fed MG on a tripod firing 30-06 or 8mm Mauser and you can rain hell down on incoming troops at 2000 yards.

People talk about how the WW 2 German army with their bolt action rifles weren't really outgunned because individual rifle fire was secondary to the MG. That was true of the USA too just not quite to the same degree.

Even look at Afghanistan today. A dozen fighting men can be engaging the enemy with 5.56 weapons but once you bring that M240 into the fight shit changes in a big way