>>717850916 (OP)
A) It just barely edged out the Gamecube, so it didn't have as many eyes that were exposed to it, especially compared to the PS2
B) It had a respectable number of really good exclusives, but a lot of them were new IPs, were series that didn't continue into the 7th Gen, or weren't attached to a big team that would expose people to the game if they looked at their back catalog, so there's not as much as a lead back into them like the Gamecube
C) Barely any of the good exclusives for the GCN and PS2 were ported to PC at any time (whether in its lifespan or even after), whereas it was pretty typical for Xbox. How many people at this point properly know that KOTOR is actually an Xbox game?
D) A lot of its strength was also tied up in the fact that, unless it was a game hyper optimized for other platforms (looking at you, MGS2), the Xbox version of multiplats were often the absolute best with more content. In retrospect, this doesn't mean much, as a lot of the multiplats are on PC, or people are fine playing the GCN versions on Dolphin with higher render resolutions
E) Another strength was its easy ability to softmod it. This was genuinely a selling point to a decent number of nerds back in the day--hell, it's the reason my Dad got an Xbox--but the context for why a softmodded Xbox would be useful is strictly in the 2000s
F) A lot of nostalgia is also tied to online, which has been shut down for ages, and it's not like you can just whip out MechAssault and play online at any time on Insignia like you could on Xbox Live
tl;dr Doesn't have the same boons to help keep it relevant as its competitors, and a lot of unfortunate "you had to be there" answers for anyone wanting to go back to it now
But fuck all the haters. Xbox rocks. TJ&E3 kicks ass if you can stomach the cringey cutscenes (which you don't get if you play the Dreamcast beta version but uhhhhhhhhhh shut up)