They don't really have anything in common when it comes to bitcoin adoption, especially when their government doesn't invest some of the country's money in bitcoin, but Singapore's resources are very likely.
Maybe just a matter of time?
If we talking about matter of time, then the other countries will be same too. We're only need to wait until Bitcoin price already very high and it's less volatile, this will make many governments will dare to accept Bitcoin (but it doesn't need to be as a legal tender).
You're wrong by saying Singapore is the most Bitcoin friendly after El Salvador, but the correct is Central African Republic.
El Salvador has clearly accepted bitcoin in its entirety in his country, even offerings related to taxes and citizenship are a company dream.
The question is whether everyone who works in the company will be granted citizenship, or only a few people?
Because as I know, it's difficult to get citizenship, because every country has its own rules governing the matter, or this rule doesn't apply to El Salvador, Please correct me if I'm wrong
You can get the El Salvadorian citizenship by just live in El Salvador for minimum of 5 years, swear a loyalty oath and doesn't have any criminal activities for a foreigners [1] I think it's not hard, but you need to be patient to wait for 5 years.
[1]
https://en.wikipedia.org/wiki/Salvadoran_nationality_law