If I understand correctly, you are not trusting "someone", u are trusting the network itself. Imo no different than any other operation on the network. Any operation on the network requires trust that the network will do what it agreed it will do.
Staking pools are not part of the Ethereum network protocol - they are a third party that you need to trust with your Eth. You are lending your Eth to this third party, who will then participate in the Eth network on your behalf, and who is also under no particular requirement to do what they say they will.
If I have to give my currency to a third party who will then invest it for me, then why bother with decentralised cryptos at all?
>any operation on the network requires trust that the network will do what it agreed it will do.
If I were an Eth apologist, I would explain how the code that defines the network operations is fully open and inspectable, so no trust needed.