WOW. That looks very impressive !
When I look at these cool images it seems to be easy to paint them.
Maybe it's easy for someone who already has experience.
However, on the other hand, it does not have to be so difficult for someone who doesn't know how to paint.
I think the keys are step-by-step instructions - in the sense of some general vision, sketch, shadows, color assignments, etc. and of course willingness.

I would like to try to reproduce something.

Maybe some turtorial for readers ?

This is what I managed to sketch one day by following the instructions by @kaylinart step by step. 😉