Because they weren't. The exact same art techniques used for 320x200 res games have been used for centuries in other media. Pixel art was most like tile mosaics, which also use dithering, and around for millennia. We designed pixel art that way not because CRTs looked like that, but because we had to pack maximum communication in those pixels. Yes, CRTs had a softening and blurring effect. We didn't really talk about that back then because it was obvious, and it wasn't something we had the ability to turn off or on, it was simply a fact of the technology.
No one designed differently for monochrome monitors with higher resolutions, or for the nascent LCD technologies of the day either. Every single article that says what this article says is literally just inventing a story.