According To expect they always say blockchain can never be hacked and your information can never be stolen .. But day in day out Hacker are hacking crypto exchanges to steal people asset , ETH Suspended hard Fork because of security reason . HitBTC and Cryptopia are understand maintenance because of hacker . Are they Using block-chain technology to deceive Us ?...
You are a little confused. Blockchains do not hack. They can be attacked, but not hacked.
In the cases you have listed, we have:
- for exchanges - the site security system was hacked, as a result of which the attacker was able to withdraw funds;
- for Ethereum hardfork - it was postponed due to a bug found in the update code (to fix it).