I don't think the effort needed to get everybody onto Bitcoin. They only had to get enough people to use it to start a network of customers, vendors, and suppliers. There may be enough Bitcoin tourists to maintain some level of use.
Having said that, I think the greater benefit is introducing crypto in general. HBD, USDC, and Tether are probably better suited for everyday commerce and remittances. If the Bitcoin experiment was a gateway to exploring other cryptos, I think it will have succeeded to some degree.
Yeah I have heard Tether has been used more in El Salvador. I would have to go investigate for myself.