3.7M is basically nothing for a country. El Salvador's GDP is $74 billion, so this is 0.005% of it.
And this gain does nothing unless the BTC is sold, and the proceeds benefit El Salvador in some way. This also assumes that amount of BTC can be sold. They need to find an entity that will send them ~$120M for their BTC, and better hope that this won't crash the market.
And, all this has to be compared with what could have been achieved with a more typical investment (which would likely have carried less risk) over the same period. If they can make 4.5% speculating on high-risk commodities and 4.3% with low-risk lending to stable businesses, it's much more responsible for a nation-state to choose the latter.
Could literally just sell that on one of the major exchanges over the course of a few hours
I've sold $8M on Coinbase Pro within minutes by setting a limit order (not a market order - although I'm sure some people will reply without knowing the difference) and it didn't impact the price
It would be an over the counter sale. Even using an exchange directly, together Coinbase and Bybit are trading $1B/day BTCUSD - there's no shortage of buyers.
And this gain does nothing unless the BTC is sold, and the proceeds benefit El Salvador in some way. This also assumes that amount of BTC can be sold. They need to find an entity that will send them ~$120M for their BTC, and better hope that this won't crash the market.