>>717791251 (OP)
a.) Ultima completely and utterly shat itself in the name of innovation without good direction, killing that series off hard.
b.) Enix got to keep making relatively safe titles, even if they made evolutionary jumps each generation, and had a highly consistent if not outright growing audience in their homeland versus the actual costs it took to make the games (at least, before XI, not sure how that goes).
c.) By being so safe but now being spaced out in years between each major title, it has plenty of breathing room to not skullfuck itself or self destruction on ambition, though XII is not looking good with its development hell collaborating alongside the whole 'we wanna shake things up' design approach they claim.
You can direct this at Wizardry as well, that series didn't implode the same way as Ultima did but it definitely fell off everywhere outside of Japan because it simply stopped being serviced and got left behind- and then Japan bought it and they've been almost entirely east-side ever since besides the occasional release or the gacha game.