Blockchain is surely technology that keep Bitcoin adoption at high level. To record some transaction into the Blockchain, everyone on the network need to verify that transaction, so basically Blockchain is a list of verified transaction by miners. Blockchain is composed of blocks where each block is attached to previous block adding the hash of the previous block in the current and so on.
Blockchain we can observe as a large data base, or ledger where all the miners have a copy of that ledger, so no one can change transactions. So blockchain is immutable, and its guarantee a security and its prevents malpractice because if someone wants to alter some transaction, he need high computational power, because he need to change all of the transaction that ever happen. To make a resume, once recorded transaction can not be changed, and this is affecting the amount of trust towards this project.
The real question here is comparison democracy to some centralized power. What makes democracy so trustworthy? The good known fact is that everything in Bitcoin protocol is open source like programs for mining, majority of the source code, which means that everyone can go through, inspect and modify the source code. As everyone can do anything, we can see that the wrong intention in this project are discarded. Of course that there were some tries to implement malware but it depends on the protocols and standards which are deciding if it is indeed processed or not.
Nevertheless, consensus between Bitcoin community is making the Bitcoin such great and trustworthy.