Infiniti made the mistake of letting its second-in-line creep into the flagship so today's Q70 ended up in no-man's land. They wanted the M to be more competitive but ended up making it too big and powerful that eventually dethroned the Q. It's like Mercedes saying "screw the S-class let's just make a really big E-class LWB". Although to be fair, the main problem has always been that the Q45 didn't achieve the level of success LS enjoyed.
The Q45 never had the marketing, or firm design-intention, that the LS had. The original 1990 Q45 was far more sport-oriented than the original LS, with more power, firmer suspension/underpinnings, firmer seats, a lack of wood-trim inside, somewhat less sound-insulation, and more responsive handling. It basically sat in showrooms and didn't sell, while customers flocked to the LS. So, the 2Gen Q45 attempted to address that, with a smaller engine, less power, richer trim inside (including wood), somewhat cushier seats/suspension/underpinings, and, in general, a higher level of comfort. There was even a version (Q45a) with an electronic, active-suspension. No dice. The 2Gen basically sat in showrooms, just like the original one, because by then, the LS, helped by clever, soothing-voice TV ads by James (Mr. Lexus) Sloyan, had become not only the very definition of the quiet, well-built, comfortable luxury vehicle, but practically cult-status as well. So, for the third (and last) generation of the Q45, Infiniti essentially did a compromise between the first two.....and still no sales, even with 10K or more discounts. I remember, when I was at a local Infiniti shop back then doing a review, they told me they were asking 38K for 54K Q45 in the showroom....and they still couldn't move it. Little wonder that Infiniti finally gave up on it in the U.S. market.
To this day, even in the D.C. area, where almost everything sells, I know of just one person who actually bought
a Q45 (a old co-worker of mine from before I retired)....and he bought a used one.