I know a bit about sport in Asia (although the first thing to get right is that "Asia" is huge, and very diverse).
To generalise wildly.
Sport per se is not as significant part of popular culture as it tends to be in Anglo-Saxon countries. Professional sport even less.
The sports that are the most popular in terms of spectator appeal tend to be the ones that are good for gambling on.
In most of the countries that have been mentioned as potential rugby competition hosts, there is a paucity of rugby grounds.
And in virtually all, if not all, of the countries that are spruiked as potential rugby friendly, there is very little, if any, organised rugby being played. And when there is, it tends to be dominated by expats, particularly at the admin level.
Just a couple of other observations. Singapore hosted the Global Tens. We happened to be there a week or so before the event, there was a bit of street advertising. It drew a derisory crowd, in a top flight air conditioned stadium.
Professional rugby exists in Japan because, for some arcane reason, big corporations get a lot of "face" from having a competitive rugby team.
Other possible entrants in a new competition, Tonga for example, do not have adequate facilities, two stadiums, both pretty primitive, frankly (although this could have changed in the 20 years since I spent time there, although I doubt it). And Tonga is an economic basket case.