It was both reasons! The highly detailed textures in the original were very heavily based on photographs, basically textures lifted from the CSI games. It added a really satisfying level of busyness to each screen, but when we tried to actually up the resolution and light it, as you guessed, it didn’t work that well. It ended up looking “old” instead of “a cooler version of what you remembered.” So we opted to simplify textures but add more detail to the scenes themselves, and also looked at how hit the road and Steve’s paintings handled “stylized” dirtiness. We also did want the game to be more of a piece with the other two seasons, while still having its own feel. So the overall density of environments and amount of caked on dirt, graffiti, and gunk is still way higher than in the other games. It also has film grain on by default, heavier vignettes in the corners of shots, and is color graded more aggressively into gunky “old film that’s been left out in the sun” tints, especially in the dark areas of shots.
And for what it’s worth, the first two seasons were also not direct uplifts of their original styles. With season one we really looked at hit the road and the covers to the comics for inspiration, and wanted that season to feel closer to those than it previously had. So it’s pretty bright, has lots of high contrast spotlights, and is a little more flat. For season two we wanted things to feel a little more like a monster movie, so there is more underlighting coming up from below. We also decided season two would have a lot of two-tone lighting so many scenes are lit above with one color and below with another. For season 3 the goal was basically, try and make it feel like season 3 but more polished, while keeping it stylistically in line with the other two seasons, so the trilogy as a whole feels cohesive even if each individual season has its own mood and details. It’s definitely a more noticeable change with season 3 since it had more of an overt style to begin with than the previous two. (Or maybe more accurately, all 3 seasons had a style but season 3’s managed to actually punch through and be noticed to a greater degree than the other two.)