Back to my question, this year has seems to be the worst year for the crypto space, Duelbits hack, Binance hack, many more hacks that happened on the space. My question is: does it mean that no one can outsmart those hacker?
Outsmarting the hackers is something that happens everyday, otherwise, you'd be hearing news of hacks everyday. Do not think that the success rate of these hacks is as high as the actual probes and attacks that these platforms resist daily. It's just that once in a while, a hacker discovers what the exchange or protocol either overlooked or didn't know was there.
Why is it that their major targets was on well know sites?
That's because the money is in those popular plaforms. They have to go throuigh those sites to reach the money.
Does it mean that no one can develop a stronger security measures to outsmart those hackers or does it mean that most of the hacks that is happening are from Insider? Or maybe someone who is already in the system are leaking out their information to hacker ?
Someone can, and they actually have some platforms that the hackers have so far been unable to breach, but we don't really count on that. Hacks are not necessarily from the "inside" although the humans are also a weak link in the security chain. A weak password, a breached or partially implemented protocol, social engineering are all vectors that can be exploited by a hacker.
Again, how do you trust the people that are being employed to work with most of the exchange or gambling site? What are the strategies to ensure that the staff they are hiring is trusted and can not compromised their duties or works, because it's always said that only those who are Inside that can know the way about the system.
You vet them to make sure they have no affinity to organized criminal syndicates. Hackers do not necessarily need staff of an organization to attack it. They have several attack interfaces to probe for flaws.