Staked ETH on Coinbase earning less APR?

Hi all, I know very little about crypto in terms of what it means as a tool for web3 or other functionality. I’m just a guy who got interested in investing in general during covid and I have a little money set aside in stocks and crypto, with ETH being my biggest holding.

I understand ETH is an improvement over Bitcoin and that ETH2 is supposed to be more energy efficient, and that’s about the extent of the knowledge I have, but I’m open to learning more.

When I originally staked, the APR was 5%. Sometime last year it dropped to 4% and then down to 3.67% now. Is there a reason for this?