Not to mention that holding bitcoin is not going to solve any problems. El Salvador is a good example here but not in the way you think. First of all they didn't become "a rich country", they just started fixing some of their problems over the past couple of years and it wasn't really because they started adopting bitcoin! It was because they started to actually solve the problems. For example they fought the corruption, the criminal gangs, etc. started improving their security and attracted foreign investors and stuff like that. With all these hard works, they managed to solve some of their many national problems.
An in charged government in a nation can not 'bet' all national money in Bitcoin investment. We know the saying "Invest what you can afford to lose" and surely a government can not afford to lose all of its national money in Bitcoin investment. Even they think and believe that Bitcoin is a safe investment asset in long term, there is risk and it is known by Bitcoin market cycle history that price can be corrected 70%, 80% from ATH.
Even if a government hold bitcoin for a long time, get profit, it does not improve economy in that country. While in a country, there are many other issues to be solved or improved partially and Bitcoin can not help a national government to do this.