There is actually an explanation that isn't just "too boring/European".
The author didn't want to change the characters for a long time. The comics contained, alcohol, guns and smoking. For some reason, America was somehow worse than the Brits (IDK how the fuck that was possible) when it comes to printing shit. I think he ditched the cigarettes and tuned down on the morbid illustrations (hanging ropes and coffins), even if it's not explicit, it was enough for getting the comic rejected in many places and with the brain rot cape shit, it was hard to compete.
It's weird how the most iconic "wild west" comic never got an audience in America.