... but it was neither as massive nor important as AI techbros claim.
It's biggest haters were (and still are) fine art elitists. You know, those grumpy men, that will scream at you for using watercolors instead of oil paints, or claiming anything not fine art (e.g. anime, comics) is not art at all. Collectors hate(d) digital, as you cannot trade JPEGs and PSDs for good money, nor early digital artists had the name recognition to inflate said prices if they could do as such.
The other part was it's mere inaccessibility due to expensive equipment and software. Back then, you only really had Photoshop (or Paint Shop Pro if you were adventurous, or Manga Studio if you knew about it and wasn't scared away by its name), which still lack support for things like rulers, so you had to use its vector graphics capabilities to get around them. This was combined with PCs that couldn't physically handle more than 4GB of RAM even if they tried, all with dual core at a long time only being an option on specialty workstation/server motherboards with 2 CPUs. This was also all before better pen tablet options. First you either had a Wacom with a screen, a Wacom without a screen, or some rebranded horror made by KYE (Genius, Trust, etc.), all while the Wacom tablets monopolized battery-free tech through patents and KYE had to rely on AAA batteries. Once we had XP-Pen and Huion with batteries (often AAAA, that are hard to obtain), we finally had some more options, but those were less available in computer shops. But once the Wacom patents expired, the lower-end tablet market become blossoming, then Manga Studio rebranded as Clip Studio Paint, and also Krita became mature enough for general use (both of which have proper on-screen ruler support). Nowadays those alternative manufacturers have even eating into the more professional market of Wacom, all while KYE have mostly disappeared from that market save for remaining stocks.