Unfortunately while the Bitcoin network is decentralized, its price is somewhat centralized. I believe that the jump from $10.000 to $20.000 was centralized manipulation, and some parts of the bear market after that. It was basically a giant Pump & Dump scheme. Now people want the crypto to go back to the Moon, but obviously this is not the best thing that can happen 
Otherwise blockchain is just a fancy database. Normal centralized databases are simply files located on a single server. Or few servers, but only for backup reasons. There is one owner of the database who can change it every time he wants, he has the control of the data. In blockchain we don't want anyone to exclusively control all the data and that's why it is designed as a decentralized database - database that exists on many locations at the same time, but is designed in a way so that any person owns only small fraction of it - his own address.
Otherwise blockchain is just a fancy database. Normal centralized databases are simply files located on a single server. Or few servers, but only for backup reasons. There is one owner of the database who can change it every time he wants, he has the control of the data. In blockchain we don't want anyone to exclusively control all the data and that's why it is designed as a decentralized database - database that exists on many locations at the same time, but is designed in a way so that any person owns only small fraction of it - his own address.