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.
Well their initial plans for buying bitcoin didn't worked as plan but then they made the right approach, being among one of the first countries recognized for owning Bitcoin as a reserve is a big advantage to the country, they might not benefit from it now since it's in reserve for the future but later on when they've reserved it for decades, they'll begin to enjoy the benefits of accumulating it now for the future, this is something other countries too that wish to boost their economy in the future should emulate and it's good that the government of Phillipines has taken that bold step in trying to buy such amount of bitcoin to reserve for the future.