A tail rotor is just a simple variable pitch propeller, and not even a particularly big one. Once you solved the problem of having a practical main rotor, the tail rotor is just an afterthought. In fact if Igor Sikorsky did anything revolutionary in his designs, it was that he realized that something as simple as a tail rotor could save you a second main rotor and all problems associated with it.
As for the second part, I think you are giving Sikorskiy too much of a credit. By the time he flew his famous VS300 (1939 to 1941) (1) there had already flown in France, the Brequet-Dorand 'Gyroplane Laboratoire' with a set of two coaxial rotors and in Germany Focke-Angelis FA-61 with two separate rotors on outriggers. Also in Germany, Anton Flettner was making good progress with his design of a helicopter using two intermeshing rotors while in the US Bell aircraft was experimenting with its own helicopter, the Bell 30.
By the end of the war, Sikorskiy had delivers 29 units of its R4, the first operational helicopter. But Flettner was a close second with his Fl282 Kolibri (hummingbird) navy observation helicopter. (Some sources even suggest Flettner beat Sikorski to the order for the first production helicopter). Focke Angelis was running a pre-series of its Fa223 6-person transport helicopter. In America meanwhile Bell was developing its own model 30 research helicopter into the model 47.
Development of the French Breguet-Dorand was ended by the Nazi invasion of France in 1940, so we van only guess what Breguet could have accomplished by 1945.
All this to say that although Sikorsky DID do a good job in developing the modern helicopter, he was barely alone and if an Alien Space Butterfly had flapped his wings on a different side of the mountain, we might now celebrate Louis Breguet or Anton Flettner as the true father of the helicopter and remember Sikorsky as that guy that mage a fortune building flying boats ant when then lost it all trying to build a practical helicopter.
EDIT 1: 1) In fairness it should be said that Sikorsky did not fly his first practical helicopter until 1940, not 1939.
Thank you for all that information. Solid research

for which I am grateful.

AISI however, Skippy the Alien Space Bat would essentially have had to do away with WWII to allow Breguet, Flettner, and for that matter Bell to become the big helicopter pioneers of human history. At least in the 1940s, which certainly had more demanding calls upon the aviation industry.
But even then, with a peaceful 1940s, its more likely that Sikorsky at the minimum becomes the Louis Bleriot or Glenn Curtis of helicopter developmental history. After all, twin-coaxial rotor aircraft represent a technological dead end until science reaches the point where aircraft like Chinooks and Ospreys become practical, and the latter itself is really a VTOL, not a helicopter.
Is there anything that reports on the maneuverability of Breguet's and Flettner's works?
Special Note: For purposes of full disclosure I should state that I grew up in Stratford, Connecticut (my hometown). In the shadow of Sikorsky Aircraft as it were. I saw Igor Sikorsky himself when he often officiated at the annual Barnum Festival parades in Bridgeport and participated in the Memorial Day Bridgeport Airport airshows. I was also there when after his death that airport was rechristened Sikorsky Memorial Airport.
So yes, I freely admit I am prejudiced







when it comes to Old Igor.

He is my hometown's greatest claim to fame. Unless you want to count Gustave Whitehead's 1901 "flight". And frankly, I DON'T.

Document your work or else it doesn't count.
EDIT 2: Like pretty much everyone else, I credit the Wright Brothers for the dawn of aviation. Everything before them represented uncontrolled flight that would lead to the inevitable crash.
The so-called "Whitehead Flyer" replica created back in the 1970s used a modern day ultralight engine. Even Whitehead's proponents freely admit that they have no idea how Whitehead's engine worked, how it was designed, how heavy it was, or how much horse-power it could generate. Nor do they offer a plausible means by which Whitehead could avoid his own "inevitable crash".
EDIT3: So for my part, I am NOT a "Stratford Exceptionalist"

