if someone bitcoiners will withdrawn there bitcoin and turn into fiat money the crypto market will not be empty because there are some new investor join and turn there local currency into a bitcoin.the new investor will attract because of the biggest value of the bitcoin.we know that the statistic fundamental of bitcoin will pump & dump, if they found out that the value of its bitcoin became higher ,they will attract and invest more and more digital currency, the old investor turn back there money to btc.the scenario are always disame vice versa, there are investor out and more investor going in because they know they have a future in bitcoin.