- Decentralization is a key part of building trust in the blockchain network, and mining helps it happen. There isn't a single point of control like in standard centralized systems. Miners check activities as a group, and a distributed network helps them come to an agreement. There is no longer any need to accept a central authority.
It's be noted that not all Blockchain are entirely decentralise while others are more centralise than others. Bitcoin uses pow mechanisms which is makes it totally decentralise and not like others that use the PoS ( proof of stake), POA (Proof of Authority) and others.
They are other POW Blockchain but are not as secure as Bitcoin and so they have been affected with the 51% attack example are bitcoinCash and bitcoin gold and others. The 51% attack is not possible on Bitcoin currently because the cost to get the computational power and resources to successfully affect Bitcoin is not feasible and this why we can say its impossible for the 51% hack to affect it. While others of the PoW Blockchain still suffer this, is because their number of miners are small comparably to the Bitcoin network.