3DS stumbled out of the gate and got better as time went on. And the third parties still supported the system. Kingdom Hearts was followed up with Bravely Default Series and Theatrhythm, Calvin followed up with resident evil and the monster Hunter series, and level five great suppertrd 3DS with the Yokai Waych series, Layton, and Fantasy Life. To be honest, I'm not even sure what you're getting at in regards to Japanese developers and 3DS: they stuck around. And we don't even know who is or isn't committing to Switch launch (well we know EA isn't but that's it).
Kingdom Hearts was followed up by no new Kingdom Hearts game - Bravely was in development concurrently with it. DS had several Kingdom Hearts games, 3DS only got one. Actually, Square Enix's 3DS support has nothing on how many games and followups they put on DS and PSP.
Capcom never followed up on those two initial Resident Evil games, Revelations 2 didn't come to 3DS.
Konami did a Konami - but I bet they wouldn't have had 3DS been a large chunk of their revenue. They were initially a big supporter of the 3DS, even commissioning a bigger-budget RPG from Tri-Ace.
Namco didn't followup on Ridge Racer, Ace Combat and Tales -- had those games met their sales expectations they would have. PSP got a Ridge Racers 2 and several Ace Combat and DS got several
original Tales games, not a cheap port of a mobile Tales game. Had Tales of the Abyss performed well on 3DS it wouldn't be hard to imagine 3DS versions of Symphonia and Symphonia 2, or even an original Tales game like the DS had. Instead Namco shifted focus back to PlayStation.
Koei Tecmo didn't followup on Dead or Alive Dimensions.
Level-5 did a great job supporting 3DS, but they've sensed the decline and have openly stated that they
will not be supporting Switch at launch; massive contrast to how they saw 3DS as an opportunity to win out the gate with Layton 5.
Note how other publishers basically didn't even bother supporting 3DS with the kind of games they made in the previous generation, games and risks that were sustainable to produce back then but weren't in the 3DS market. Sure, the biggest games remained on 3DS, like Monster Hunter, Yokai Watch, Shin Megami Tensei but it's evident that as the market shrunk, and so has the variety and type of games that were produced for 3DS and Vita. Both systems' libraries don't hold a candle to their predecessors, and publishers definitely didn't greenlight followups for most of their original games.
Before the 3DS launched, the message was that it was *the* flagship platform for a lot of publishers' IP to launch on. Many of those IP never returned after the initial commitment, which is indicative of the way the market went and how 3DS wasn't a sustainable enough of a platform for bigger budget handheld games and risks. Also remember how 3DS - as originally intended -- didn't even support DLC. DS represented such a massive chunk of the Japanese market and for third party publishers that supporting Nintendo's followup out of the gate would be irresistible. The pieces didn't come together so well though so few of those initial big budget handheld games got direct followups greenlit, and publishers moved those IP elsewhere.