I doubt that this is even remotely accurate. Even the slightest bit of critical thinking quickly dismantles that “belief”.
https://en.wikipedia.org/wiki/Richard_Jordan_Gatling#Gatling_gun
In 1877, he wrote, “It occurred to me that if I could invent a machine gun which could by its rapidity of fire, enable one man to do as much battle duty as a hundred, that it would, to a large extent supersede the necessity of large armies, and consequently, exposure to battle and disease would be greatly diminished.”
Why would he not realize that countries, generals, kings, and those in power would simply send more men to die? They will not send 2 guys with a machine gun and then simply accept that the battle was lost if their guy loses. No, they will send a million men, as many as are needed to take another foot of ground.
Colonialism was super popular, so a couple of dudes with machine guns could mow down a field of natives with much less risk.
Plus a machine gun is much more impressive than some dudes with single fire guns. A platoon (or whatever fits on a boat or three) can be overrun. Throw a couple of machine guns in with a couple of brutal shows of force and you got yourself a colony.
WW1 was still a ways off and it wasn’t really the target market for your Gatlings and Maxims.
Maxim’s inspiration:
“I was in Vienna, where I met an American whom I had known in the States,” Maxim told the Times of London. “He said: ‘Hang your chemistry and electricity! If you want to make a pile of money, invent something that will enable these Europeans to cut each other’s throats with greater facility.’ ”