El Salvador made the mistake of thinking that bitcoin could save their economy and they got too dependent on it, but I don't think they made any mistakes with their bitcoin investment strategy.
I have been active in the thread about El Salvador making Bitcoin a legal tender and I don't think the country bought Bitcoin because they wanted it to save their economy maybe from collapse. They just had a comprehensive plan that includes a bitcoin city which comprises several projects like mining facilities, hotels, resorts, etc. Sadly, the country couldn't go ahead with these projects, but they kept buying Bitcoin. El Salvador’s Bitcoin investment has been profitable, and it seems they have a long-term approach.
I'm also not saying they invested in bitcoin with the intention of saving their economy.
If I remember correctly, they made bitcoin legal tender when their economy was facing many challenges and it seemed like they had no viable solutions left. They decided to make bitcoin a legal tender and set the expectation that bitcoin adoption would be able to improve their economy. But we can be seen after 4 years of bitcoin adoption like using it as currency, bitcoin cities, or efforts to attract foreign investors through crypto-friendly policies. Their economy is getting worse as they are on the brink of default and had to accept some demands from the IMF to get a $1.4 billion loan to save the economy.
It can be said that in the past 4 years, they have bet big on a plan to rely on bitcoin and crypto, but it seems that things have not turned out as they expected.