Is it possible for him to become that rich in such a short time
Yes nothing is impossible with bitcoin when it comes to financial investment, El-Savador whole story about debt might have been cleared right before that eight years you thought, one thing with bitcoin as an investment is that it secures the future for you, there's no how you could make an investment in bitcoin over a long duration and never have a reason to smile at the end, it appreciate, its a digital good store of value, its an investment asset, its secured, its anonymous, if you look at the the history from how it all started from 2009 till date then you could get more conviction that El-Savador or you could achieve a big dream with bitcoin adoption and investment.
I certainly agree, and what was the whole excitement about for Bitcoin enthusiasts back then when El Salvador took this step? Apart from we now have a country that has made Bitcoin a legal tender, the belief was also, like anyone that has been investing in Bitcoin from the beginning, making a profit, in the long run, is also the target.
As the article stated if the Bitcoin mining company powered by the geothermal energy of volcanoes are actually operational wouldn't this generate huge profits for the country down the years? I believe your guess is as good as mine, however, whether this will make El Salvador the richest country in the world in 8 years time I doubt but will definitely set the county up well.