Decentralization is not an end in itself. It serves Bitcoin's main purpose - cash-like on-line transactions. To be cash-like, Bitcoin was implemented as a decentralized network of nodes. To be reliable, each node independently verifies every transaction before committing it to the permanent transaction history. Without cooperating, every node makes exactly the same judgment about every new block and all the block's transactions. There is no democracy, no voting. As long as all nodes arrive at the same transaction history, Bitcoin keeps working. Bitcoin even tolerates some nodes diverging from the common transaction history. Those nodes cease to participate in Bitcoin. The Bitcoin network operates as a supermajority - every node independently discovers the same transaction history

The Bitcoin price market, and the distribution of ownership, are separate from Bitcoin. Nothing in the code which runs a Bitcoin node has any control over who owns what quantity of Bitcoin, or how much fiat money was used to buy it. These markets may or may not be corrupt, or may become corrupt in future. Bitcoin does not care. Nobody who operates a Bitcoin node would ever demand that Bitcoin's node software should be modified to prevent price manipulation or concentration of ownership

The other side of decentralization (and the supermajority) is that every software change must be adopted by every node. Or, enough nodes must upgrade to accept a software change such that Bitcoin is still effectively decentralized even if its node network shrinks substantially. This is a disincentive to making changes. The most recent urgent change was in 2013, when the network was still small enough to be considered centralized