Someone said its as a result of crypto founders /devs being inexperienced. Uuhm in a way, that is right, but sometimes, we the users are also making the mistakes.
There are scammers out there, a lot of them, and some of us are so careless that they cant even make a good research before investing their money in any exchange, ICO or whatever it is, they just carelessly invest their money without minding and at the end the scammers will make away with it.
No matter how secure we develop our systems, hacker and scammer will always exists and will exploit any loop hole in the system. Even the exchanges themselves do scams and run away with people money.
Being an individual it is our responsibility to follow every principle of security and use all the security measures like 2fa, strong passwords etc.
Also I think that his number of stolen crypto will increase as more and more people will come to this industry, so more the chances of hackers to hack people money who are careless with their efforts and accounts.