Here's a super simple explanation. Pantone is for print. RGB is for screens.

Screens "paint" with light. Printing "paints" with... well paint. Pigments.

Light makes things lighter (addetive). Your black screen lights up making up a picture.

Printing makes white paper darker by putting paint on it (subtractive). It's a fundamental difference.

There's a lot of science that goes into this, but that's the most ELI5 as I can make it.