If the market is small and saturated by other companies with a long history in the community you have to come in with something really strong to get noticed. 5e, on it's own, is not strong enough. That's why there's a Commercial for it, but very low interest in the localizations, comparatively.
Gotta know your market, y'know?
If WotC -did- want to bring 5e to Japan in a big way, they do it with a Storefront rather than Books on a shelf. Something that is a whole experience wrapped up in one shot that you don't have to take home to try.
Maybe hire some DMs to run games in rolling shifts of a giant West Marches game that "Everyone is playing in" in a restaurant environment with D&D themed foods and drinks for the customers. Each West Marches game session could be recorded for replay and given to the customers as an audio file or something for a nominal additional fee to pay for the Thumb Drive or whatever. You'd get the One-Shot, the "Night Out" vibe to kill the living space issue, and provide food and drink to keep your customers playing and paying.
Hell. Run it as a "Fancy Restaurant" you have to get a reservation for to give the DMs time to prep specific scenarios for specific parties. Then have "Scenario Menus" where the restaurant keeps a series of one-shots and scenarios on hand for when a group comes in wanting to run their own adventure in the game, like Adventurer's League content.
Add in some fancy looking boffer weapons and encourage the patrons to lightly swat each other when someone makes a bad joke, or otherwise build up some themed traditions for the players to latch onto to create a sense of community...
That might do numbers.
To be clear, I live in Japan, and I've been to Japanese gaming stores. It would be incorrect to say 5e isn't present in Japan, it does actually have a fairly prominent placement in the stores I've been in. At the same time, it's just
one of the big boys, rather than THE TTRPG.
As you mentioned, the way Japanese people play TTRPGs tends to be different from in the west. Long campaigns aren't popular, likely because of the time constraints of Japanese jobs. I would guess this is another reason for CoC's popularity, as it simply lends itself better to stories that begin and end in one night. The "replay" scene as mentioned is a vital part of the TTRPG community here, and in recent years that has expanded to youtube. And now of course there are also livestreams of TTRPGs, often played by youtube vtubers.
I would mention another potential obstacle for D&D is the price investment, it costs quite a bit just to get a D&D game running. The aforementioned
Sword World is sold in 3 books representing different tiers of play, basically similar to the old B/E/C/M D&D format. It's sold in a very small A6 format (basically the same size as a small manga) with minimal manga-style artwork in B&W. The first book costs about $8. That's a super-small investment to start playing a TTRPG.
BTW, I highly recommend checking out Sword World if you're interested in TTRPG history, it's fascinating as an example of parallel evolution. There are no official translations unfortunately, but there are fan translations of the latest editions. The game started as essentially a D&D clone (the original Lodoss campaign was OD&D I believe), with small changes to make it more palatable to a Japanese audience. For example, the game ONLY uses d6 dice, you essentially roll 2d6 for everything, and use "power tables" to convert the results to different numbers. d20 and other polyhedral dice weren't really available in Japan in the 80s, although you can easily buy them now. Despite starting as a D&D clone, it's extremely different from modern D&D, the class system is essentially a skill system now, each level in a class essentially just gives you a skill point in particular skills. It also has some really neat rules for simplified/TOTM combat which are fully supported by the writeups for actions and spells.