From what I remember at the time, there also was a culture shift going from text-based first to graphics-based first. One of the complaints against UMS was that kerneloops could not be displayed while X was running, because the kernel knew nothing about how to get text onto a graphics console, nor could it return the display to text-mode by itself. Whether that was just a convenient rationalization or a driving factor, I don't know.
I also think that the widespread availability of EDID was a big factor in the change: what good does it do for the kernel to switch to graphics mode if it then requires extensive configuration before it can output anything useful? There may have been earlier interests in moving more graphics output control into the kernel, but manual scanline configuration would have prohibited deployment at large-scale anyway.
I also think that the widespread availability of EDID was a big factor in the change: what good does it do for the kernel to switch to graphics mode if it then requires extensive configuration before it can output anything useful? There may have been earlier interests in moving more graphics output control into the kernel, but manual scanline configuration would have prohibited deployment at large-scale anyway.