Decentralization is based on holding a scarce resource. There are 3200 pools registered on the Cardano network, 4 largest block produces have shares of 8%, 4%, 3% and 2% of the entire supply of Cardano tokens. Delegates are participants in a cryptocurrency network, in the case of Bitcoin miners which burn massive amounts of electricity to sustain the network and provide hash rates to pools. In the Bitcoin network several largest pools such as Foundry USA provide about 32% of the blocks, Antpool 21% and 3 other pools 18%, 8% and 6%. If two dominant pools would join together the Bitcoin network could be compromised with a 51% attack and in the worst case scenario everybody’s funds would disappear. On the Cardano network the are 1.3 million stakers or delegates and the blocks produced are run by a fairly inexpensive computer or virtual machine making energy use negligible compared to the Bitcoin network. In summary Cardano is orders of maginitude more decentralized and energy efficient than Bitcoin. Read more about it here: Is Cardano A Security?