These concepts are not related.
Today Bitcoin Mining is almost centralized:
If one day all those big 4 mining pools merge, bitcoin mining is going to be centralized.
Will bitcoin not be considered a cryptocurrency anymore?
There are few thinks you need to consider. First, there are 3 main types of decentralization (
By Vitalik Buterin):
Architectural (de)centralization — how many physical computers is a system made up of? How many of those computers can it tolerate breaking down at any single time?
Political (de)centralization — how many individuals or organizations ultimately control the computers that the system is made up of?
Logical (de)centralization— does the interface and data structures that the system presents and maintains look more like a single monolithic object, or an amorphous swarm? One simple heuristic is: if you cut the system in half, including both providers and users, will both halves continue to fully operate as independent units?
Second, what is a cryptocurrency? I think its hard to define, but in a simply way we could say it's just
digital cashThere were other cryptocurrencies before bitcoin, but bitcoin was the first to survive because it was decentralized, inspired on a P2P file sharing. Thanks to satoshi who invented a decentralized consensus mechanism, the proof of work.