The reason El Salvador adopted it is to lower remittance fees. The system of banks and 3rd party overseerers resulted in large fees most weren't able to afford, and if they did, they lost a huge chunk of their money. These ATM is great step to support bitcoin.
That is without a doubt one of the reasons but at the same time there is no doubt that they are looking at the long term and they are thinking that it would be fantastic for them if people that are big on cryptocurrencies and businesses decided that they want to establish themselves at El Salvador and bring a huge deal of foreign investment to the country.
This is not a bad strategy at all and if they can endure the pressure of the international community and keep going forward with this then El Salvador could become a destination for many people that have adopted cryptocurrencies and bring great prosperity to the country.
They will always find someone contradicting their move. But once people start learning how to utilize crypto and experience the benefits of it, more than likely, they will change their stance. Some are against without basis. Maybe, they need to educate also their citizens, it may help them in further understanding the nature of crypto. All the information can be found via internet but getting it from actual talks or seminars would be helpful to some as they can directly ask questions to their authorities.