The Bitcoin features can make some believe that it will be a main cryptocurrency for the following reasons. First of all, Bitcoin is the currency of the internet and unlike real money, Bitcoins are issued and managed without any central authority whatsoever. Second, for this reason, it is more resistant to wild inflation and corrupt banks. Third, over the years , Bitcoin has consistently risen in value though at a fall at the moment,  but they believe it will rise ,that’s surely what makes people have faith in Bitcoin.
One thing should be noted – people who believe in Bitcoin the most are people who invest in /want Bitcoin.