So far the bitcoin experiment success is largely only from the tourism side.
I suspect there are other benefits not apparent yet. Remittances sent in bitcoin directly to the recipient aren't tracked (and aren't able to be tracked), when the recipient is using their own wallet (e.g., BlueWallet). Even if that level is low so-far, it will increase as bitcoin is now the remittance method with the least friction for sending money back home for the Salvadoran diaspora.
How is greater remittances sent in bitcoin a success? Because some or most of those remittances are then spent domestically within El Salvador. And that inflow of bitcoin spent locally helps a circular economy form. Which has other benefits that will be hard to track, but will be evident as the participants in El Salvador's circular economy start to outperform their fiat brethren (in income, in savings, quality of life, etc.).