"If it's decentralized, how can one person's tweets affect its price?"

I'm seeing a lot of people asking this question on social media so let's educate the people asking this question. There are no stupid questions, right?

Bitcoin, the protocol, is decentralized. No protocol change can be made to Bitcoin without overwhelming community support and anyone can submit a BIP (Bitcoin Improvement Proposal). Yes, you can do it right now.

Then there are various checks and balances to ensure that the process to determine whether the protocol change is adopted or not does not go against the wishes of the community (full nodes). The community can NEVER be forced into accepting an undesirable protocol change. This is only true for Bitcoin.

Bitcoin, the network, is decentralized. Bitcoin is not governed or ruled by miners. Miners simply find blocks. All full nodes validate transactions based on consensus rules, hard-rejecting blocks and transactions which break these software rules. Software rules with no rulers.

As long as you run a full node, miners have absolutely no power over you. There are at present 9674 reachable full Bitcoin nodes (total node count a lot higher) across more than 98 countries and 11700 nodes with channels on the Lightning network. Don't trust, verify. Run a full Bitcoin node. Run a Lightning node.

Bitcoin's price is not always decentralized, although it could be. Why? Because it would seem that most humans are sheep-minded slaves to clout-chasing government-subsidized charity project billionaires.

Don't blame Bitcoin for you being unable to think and reason for yourself. For as long as you do as you're told and fail to take ownership of your actions, you will continue to fail Bitcoin. Bitcoin will never fail you.