Back in 2021, El Salvador took the first step into making Bitcoin legal tender. It defied the establishment by proving BTC can be used as an alternative to Fiat. Set ourselves forward 4 years later, and now El Salvador is regretting its decision. It made a deal with the IMF, in exchange of limiting its involvement with the world's beloved cryptocurrency. I guess all good things come to an end.
I wonder what could've been the culprit of Bitcoin's limited adoption within the country? Was it bad planning/execution? What if El Salvador rejected the IMF's demands? Would've it survived with Bitcoin as its sole currency? I mean, the government continues to buy BTC. At some point, it would've paid off its debt. That would've help turn it into a developed country in the long run.
What about other countries adopting BTC as legal tender? Is there still a possibility? Or is it "game over"?
Your input would be greatly appreciated. Thanks.

Not failed but BTC exceeds the function limit that it should be, if it is made a currency it is too valuable, and yes most countries and people treat Bitcoin as an asset, reserve fund, or more precisely as an investment asset for long-term value growth from the attack of Inflation in Fiat.
If the country wants to treat it as a currency it can, but they think that Bitcoin is better held for long-term survival.