Poor nations can benefit from Bitcoin if they invest in it. Countries like El Salvador and Bhutan have invested massively in Bitcoin and I guess that they are now in profit.
AFAIK they have not sold their bitcoins which means you can't really say they've made enough profit to solve their problems. They just have an asset in their reserves that has appreciated in value and economic problems won't be solved just by having a valuable asset "in the vaults".
You are right, El Salvador is yet to sell but the Royal Government of Bhutan has sold about $33.5B of its Bitcoin late last year. However, the country still holds close to 12,206 Bitcoins as of last year.
https://coinmarketcap.com/academy/article/bhutan-cashes-out-dollar335b-in-bitcoin-still-holds-dollar111b-in-btcThe title of that thread is a bit misleading, and the numbers make it appear as if they sold $33.5 billion worth of bitcoin, which their entire holding has never gotten close to that volume. Now the current amount of bitcoin they hold is worth
$884,938,350. The article is a bit updated as their holding volume has reduced from 12,206 bitcoin down to 10.635K bitcoin, according to ARKM.
The Royal Government of Bhutan has sold 367 Bitcoin (BTC), worth about $33.5 million through major cryptocurrency exchange Binance. According to Arkham Intelligence, a blockchain analytics firm that tracked the transaction, the sale occurred Thursday morning when Bitcoin reached an intraday high of more than $90,000, before later retreating to $87,000.