According to information from Arkham, the Salvadoran government has earned more than US$200 million on its investments -
https://intel.arkm.com/explorer/entity/el-salvador. I don't think their experiment has failed, as some countries are unable to invest pension fund assets properly, and their value declines over time due to inflation. The Salvadoran government has shown the whole world that Bitcoin is an excellent investment asset. The fact that Salvadorans do not use Bitcoin is not the government's problem. The only thing that should concern the Salvadoran government is to start complying with the IMF's requirements, as they risk losing cheap credit.
This shows El Salvador is treating Bitcoin as an investment asset (store of value). Not as a currency. The whole purpose of making BTC legal tender was to spread its use as a currency within the country. But so far, El Salvador's government has failed in doing so. I think the main cause was a lack of user experience. People only claimed the reward from the Chivo Wallet and forgot about the rest. The reward should've been issued gradually subject to usage of the network. Sort of how like NEM's PoI (Proof of Importance) algorithm works. You need to use XEM regularly to be able to qualify for "staking".
Another thing that may have prevented the masses from adopting Bitcoin was market price volatility. Not to mention, the BTC blockchain's limited transaction capacity. Is there still hope? I'd say, yes. But it's going to take quite some time before the world gets used to BTC as an alternative currency. El Salvador might need to wait until the deal with the IMF comes to an end, to continue with its Bitcoin agenda. Patience is a virtue.