First of all hacking is a hobby but when there is too much money involved it just crooses the line for hacking to be generalized by hobby. It becomes as proffression first of all. NOW crypto currencie exchanges maintain security by seriously so they always keep the algorithm in a different by the time spend. Please note that Btc or block chain basically not getting hacked its a flaws of exchange houses and hacker break into exchanhe houses. Now to understand the relation its so hard to break the code for havker of there is only single person occupied.
So basically its done by a group of syndicated hackers which send numorous error code or signal to API which makes it confuse and hence it got hacked.
So people who are involving with these crimes they are proffessional. And yeas its a rich proffression. But without loving the proffression or works no one get succeeded.