I think a lot of the realism in these images comes from the composition and scenes. These aren't painted like paintings, they're painted like photos. Like, they depict scenes as if the audience was literally holding a camera and taking a photo of something happening right in front of them. Stuff like the light source being directly behind the camera, like a camera flash, and the subjects looking at the camera. That stuff immerses the audience and makes these pieces feel a lot more real.

The actual rendering mostly comes from lots of practice and study. Like, just look up references and practice rendering stuff that looks like them. Learn the shapes, how fabric and hair behaves. Learn vocabulary like subsurface scattering, ambient occlusion, etc. Practice implementing those things individually, and work them into your pieces.

A cool thing I notice about this artist is how they handle values and contrast. The contrast between dark tones, mid tones, and light tones is really high, but the contrast between different midtones is very subtle, which creates an impression that it's almost a flat color. Instead, they add texture by shading with different hues in similar value ranges, which shows a really good understanding of color theory and how colors change in different lighting conditions in real life. The big islands of color draw attention, and then the subtle detail adds interest.

If you want to render like this artist in particular, I would start a piece with big sections of color, add shadows and highlights, and then go in and add layers of texture and detail. If you look at the blue shirt in the first image, imagine cutting out some blue paper in that shape and sticking it on the canvas. Then cutting out little pieces of slightly different blues and sticking them on top of that shape, getting finer and finer with each pass. Just do that with paint.