liquidity is the major factor for any exchange but in order to get it you have to build trust among the traders and provide low fee or trading competition to attract traders.so security,liquidity and reward scheme can attract traders in short time .but i think there is one more factor which play crucial role i.e accessibility(desktop and mobile app) ,binance in just a few year become the most preferred exchange bcz they have everything,security +apps+low fee+trading competition.