there several instances to note here, was your account hacked alone or was the exchange hacked? if the exchange was hacked then it is of no fault of yours but if it was only your account that was affected then you must have compromised your login details which lead to the hack. things you need to do to avoid been hacked is for you not to visit phsing sites, don't use the same password for exchange and airdrop/bounty programs. avoid using same password for your email and exchange accounts and my last advice is for you to enable 2Factor Authentication in all your exchange accounts even when you don't have funds in there.