With models getting bigger with every generation and the Altima so close to the Maxima, the Maxima was bound to get forced into a corner. Nissan couldn't make it much bigger.
Whereas Toyota went the boulevardier route with the Avalon over the Camry, Nissan went Grand Touring with the Maxima over the Altima. However, how GT could they go without stepping on Infinity's toes? So Maxima loses out.
BTW, I wonder how Avalon sales compare to those of Maxima given that they were both subject to the same kind of marginalization / redundancy?
Cheers,
John M.