In 1939, Will Eisner was 22 years old. He had already established himself as one of the most successful entrepreneurs in a booming new medium. More importantly, he was pushing that medium, both through his own art and through the artists working for him. His art was always a notch above the rest and from the beginning he was creating new techniques in what we now call sequential storytelling.
Yarko is nearly forgotten now (he only made one American appearance -- Wonder World Comics #8), but it stands up better than many of his longer lived competitors.