I think the fact that Manhattan was a less mass-consumption movie might have contributed (and I don’t believe it was fully letterboxed to 2.35:1 anyways?). Spielberg was able to get a few of his/Amblin’s movies released in widescreen, even on VHS, though they were only 1.85:1 movies - first, Warner Bros. released The Color Purple, Empire of the Sun (on LD only, IIRC) and Joe Dante’s Innerspace exclusively in letterbox, then Universal used letterbox for E.T. (on LD only) and Always. I believe the first 2.35:1 Spielberg movie released in widescreen on video was indeed Last Crusade, and even then he wasn’t able to convince Paramount to release a letterbox VHS (though it was LBX on S-VHS).

I have no idea of the history of letterbox releases in Japan, but using LDDB’s dates, the next North American letterbox home video release of a scope film after Manhattan was the Criterion LD of The Hidden Fortress in 1987 (it has the earliest volume number of the three scope LBX CC releases that year, the other two in '87 were The Graduate and Blade Runner). In 1988, three non-Criterion scope LBX LDs came out - Ben-Hur and Doctor Zhivago from MGM, and Otto Preminger’s The Cardinal from Image. LBX in general, and scope LBX in particular, became a bigger thing in 1989 (Fox, Columbia, and more from MGM), and I believe all the studios were on board by 1990. (I have no idea what the next scope LBX VHS was after Manhattan - I do know there was a widescreen VHS of the 1989 restoration of Lawrence of Arabia, maybe it was that?)