Cyclo-Cross Takes Over the World!

Just a quick note to ask if anyone has an idea why cyclo-cross riders have entered the pro Pro Tour with such panache. I'm not a historian, but I can't remember a time when riders like MVDP, Wout Van Aert and Tom Pidcock won classics, stage races, and lead stage races at their first crack. I mean, we're talking about competing against the best in the world who have years of experience trying to perfect their craft. Is it mere coincidence? Should up-and-coming riders spend a few years plying their trade in the mud? As a complete outsider, I'm genuinely curious to know what people think.
Over 700 riders at WT & PCT level aren't there? I would think if CX meant anything, more names from CX would be coming through at the top of Road than those you mentioned.
I think although CX has a more technical aspect to it than road, fundamentally it's like endurance track cycling in that the very biggest engines aerobically should float to the top and be discovered early, but the pool that crosses to road is relatively small compared to that of road.